What should you focus on for a system design interview?
Which topics should you start with?
Scalability and reliability was the most common topic, appearing in 224 of 942 interviews. Its questions cover scaling, load balancing, latency, fault tolerance, and recovery. Use these checks to find gaps in what you can explain:
- Can you compare horizontal and vertical scaling and say when you would use each?
- Can you explain retries, idempotency, and event ordering?
- Can you describe how you would spot failures in a system and recover from them?
Software architecture, databases and data pipelines, and AI systems were also common topics. Alongside scaling, check whether you can explain application layers, choose storage, and discuss caching and consistency.
Which individual questions came up most?
Designing a production RAG pipeline led the list, asked in 19 of 942 interviews. Choosing between a monolith and microservices came next, followed by a tie between microservice communication and designing a public API rate limiter.
Use these questions to test how clearly you can explain a design:
- For a RAG pipeline, can you discuss evaluation, privacy, and production trade-offs?
- For microservices, can you explain where you would draw service boundaries and when migrating from a monolith is worthwhile?
- For a rate limiter, can you describe its API contract and design a data structure for a rolling window?
How much depth should you prepare for?
In these interviews, 60% of questions were senior-level and 34% were mid-level. The list includes definitions, such as MVC and UML class diagrams, as well as end-to-end design tasks.
Check both kinds of answer. Can you explain MVC or a UML class diagram in plain words? For a payment, booking, or file storage system, can you state the requirements, choose technologies, and explain the trade-offs to stakeholders?
What did reviewed answers miss?
For microservice communication, 4 of 5 reviewed answers missed asynchronous communication through message brokers or event streaming, such as Kafka.
Check that your answer covers both synchronous and asynchronous communication. Can you explain how services communicate through queues or event streaming, rather than only describing service API calls?
Should you also prepare to write code?
Coding tasks appeared in 5 of 942 interviews. Check whether you can complete tasks found in the sample:
- Design a data structure for a rolling window rate limiter.
- Extend a feature flag implementation to match attributes and use a default fallback.
- Build a chat service where a message entered in one browser appears in another.
Who gets asked System Design
The 20 most asked System Design questions
Counted by interview, not by mention: a question asked twice in one conversation counts once.
How would you design and implement a production RAG pipeline?
Asked in 19 of 942 interviews · last asked Oct 20 · Design · Mid-level
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RAG retrieves relevant documents and gives them to a language model to help answer a question. I would parse documents, split them into chunks, and store embeddings with source details and access rules. For each question, I would combine keyword and vector search, rerank results, and generate an answer with citations. If evidence is missing, say so.
- Use RAG for changing or private facts; fine-tuning mainly changes model behavior, not access to current facts.
- Enforce document permissions before sending context to the model; treat retrieved instructions as untrusted.
- Track document versions, refresh changed content, and remove deleted content from indexes.
- Test retrieval quality and answer accuracy with known questions; monitor latency, cost, and failures.
What the interviewer checks: The interviewer checks whether you can build a secure, reliable retrieval system and measure answer quality, not just connect a model to a vector database.
Other ways it was asked
- “What is retrieval-augmented generation (RAG), and when would you use it?”
- “What is retrieval-augmented generation (RAG)?”
- “How can you optimize a retrieval-augmented generation (RAG) system, and why might you choose RAG over another approach?”
How do you choose between a monolith and microservices, and when is migration worthwhile?
Asked in 17 of 942 interviews · last asked Oct 16 · Design · Senior
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I would start with a modular monolith unless there is a clear need for separate services. Microservices help when teams need independent releases or parts need different scaling, but add network and operational complexity. Migration is worthwhile when these benefits outweigh the cost and the team can run distributed systems reliably.
- Base the choice on business needs, team size, domain boundaries, and operational skills.
- A modular monolith keeps clear internal boundaries while remaining one deployable application.
- Microservices add network failures, cross-service data consistency problems, and monitoring work.
- Migrate one well-defined part at a time, with measurable goals; avoid a full rewrite.
What the interviewer checks: The interviewer checks whether you can balance business needs, team capacity, and distributed-system costs without following trends.
Other ways it was asked
- “How would you decide how to split a monolith into microservices?”
- “When would you choose microservices over a monolith, and when would you not?”
- “When starting a project, how would you choose between a modular monolith and microservices?”
How do microservices communicate with each other?
Asked in 9 of 942 interviews · last asked Oct 23 · Concept · Mid-level
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Microservices communicate through direct requests or asynchronous messages. Direct calls use HTTP APIs, often REST, or gRPC when the caller needs a response. Messages go through a broker or event platform, such as RabbitMQ or Kafka, so services can work independently. For example, an order service publishes an event that a shipping service processes later.
- Synchronous calls are simple, but the caller depends on the other service being available.
- Asynchronous messages support buffering and retries, but processing may be delayed.
- Use timeouts for direct calls and handle duplicate messages safely.
What the interviewer checks: The interviewer checks whether you can explain both communication styles and choose between them based on response needs and failure handling.
Common mistake (in 4 of 5 reviewed answers): Many answers forget that services can communicate asynchronously through message brokers or event platforms, not just HTTP calls.
Other ways it was asked
- “What are the ways microservices can communicate with each other?”
- “How do microservices communicate with each other? Can you give an example?”
- “How does communication between two microservices happen?”
How would you design a rate limiter for a public API?
Asked in 9 of 942 interviews · last asked Oct 21 · Design · Senior
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I would use token buckets at the API gateway, keyed by API key or user ID. Redis would update each bucket atomically so all API servers share one limit. Buckets allow short bursts but cap the average rate. When a bucket is empty, return HTTP 429 with a Retry-After header.
- Set bucket capacity and refill rate by user tier and endpoint cost.
- Use IP limits for anonymous traffic, but account for users sharing an IP.
- Expire idle buckets only when recreating them would not grant extra tokens.
- Choose whether to allow or block requests if Redis fails, based on availability and abuse risks.
What the interviewer checks: The interviewer checks whether you can enforce fair limits across servers while handling bursts, concurrency, and failures.
Other ways it was asked
- “How would you implement the rate limiter?”
- “How do you design a rate limiter?”
- “How would you design rate limiting for a public API?”
What is middleware, and how is it used in an application?
Asked in 8 of 942 interviews · last asked Oct 6 · Concept · Junior
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Middleware is software that sits between application parts and handles shared tasks. In a web app, it runs around request handlers to check authentication, log requests, or handle errors. It can change a request or response, pass control to the next step, or stop processing and return a response.
- Middleware keeps shared logic out of individual request handlers.
- Common uses include authentication, logging, rate limiting, and error handling.
- Order matters: earlier middleware can affect what later steps receive.
- A middleware step can reject a request before it reaches the main handler.
What the interviewer checks: The interviewer checks whether you understand shared request processing and how middleware order affects application behavior.
Other ways it was asked
- “What is middleware?”
- “What is middleware in a web application?”
- “What is middleware, and what does it do?”
What is the MVC architecture?
Asked in 7 of 942 interviews · last asked Oct 22 · Concept · Junior
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MVC stands for Model–View–Controller. It splits an application into three parts: the Model manages data and business rules, the View presents information, and the Controller handles user input and coordinates actions. This separation makes code easier to change and test.
- The Model holds application data and business logic, not just database access.
- The View displays information to the user.
- The Controller handles input and coordinates updates to the Model or View.
- The exact interaction between these parts varies by framework.
What the interviewer checks: The interviewer wants to know whether you understand each part’s role and why separating responsibilities helps.
Other ways it was asked
- “What is MVC?”
- “At a basic level, what is MVC?”
- “Explain MVC.”
What is the difference between horizontal and vertical scaling, and when would you use each?
Asked in 7 of 942 interviews · last asked Oct 22 · Concept · Mid-level
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Vertical scaling gives one server more CPU, memory, or storage. Horizontal scaling adds more servers to share the work. I use vertical scaling when a larger server can meet demand without changing the system much. I use horizontal scaling for growth beyond one server or better availability, if the workload can be split.
- Vertical scaling is simpler, but has hardware limits and may require downtime.
- Horizontal scaling adds coordination, load balancing, and data management complexity.
- More servers improve availability only when the system can handle server failures.
What the interviewer checks: The interviewer checks whether you can choose a scaling approach based on growth, availability, and system complexity.
Other ways it was asked
- “What is the difference between vertical and horizontal scaling?”
- “What is the difference between horizontal and vertical scaling?”
- “What is the biggest difference between horizontal scaling and vertical scaling?”
What is a UML class diagram?
Asked in 6 of 942 interviews · last asked Mar 27 · Concept · Junior
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A UML class diagram shows the static structure of a system: its classes, their attributes and methods, and their relationships. A class represents a type of object with shared data and behavior. The diagram helps explain how the system is organized, rather than how it runs over time.
- UML stands for Unified Modeling Language.
- A class is usually drawn as a box with sections for its name, attributes, and methods.
- Relationships include association, inheritance, aggregation, and composition.
- Class diagrams describe structure; sequence diagrams describe interactions over time.
What the interviewer checks: The interviewer checks whether you can explain classes, their relationships, and the purpose of a structural diagram.
Other ways it was asked
- “What do you mean by a class diagram?”
- “What is a class in UML?”
- “What is a class diagram?”
How do you design and build microservices?
Asked in 6 of 942 interviews · last asked Sep 25 · Design · Mid-level
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I split the system by business responsibility, with each service owning its data and deploying independently. I define clear API or event contracts and choose synchronous or asynchronous communication based on the workflow. I add automated tests, deployment pipelines, monitoring, and failure handling. I use microservices only when independent scaling or team ownership justifies the extra complexity.
- Choose boundaries around business capabilities, not technical layers; avoid services that constantly call each other.
- Avoid shared database tables; use local transactions and patterns like sagas for workflows across services.
- Use timeouts, bounded retries, and circuit breakers; make retried operations idempotent.
- Secure service access, collect logs, metrics, and traces, and scale services based on measured bottlenecks.
What the interviewer checks: The interviewer checks whether you can define service boundaries and manage the data, failure, and operational costs.
Other ways it was asked
- “What are the key considerations when designing a microservices architecture?”
- “What are some key factors to consider when designing scalable microservices?”
- “How do you design and implement microservices?”
What is idempotency, and when is it useful?
Asked in 6 of 942 interviews · last asked Oct 15 · Concept · Mid-level
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Idempotency means repeating the same operation has the same intended effect as doing it once. It makes retries safe when a request times out or a message is delivered again. For example, a payment API can use an idempotency key to avoid charging twice for the same payment request.
- Idempotency concerns the effect on system state; repeated calls may return different responses.
- Setting a value is usually idempotent; incrementing it is not.
- Idempotency keys identify retries of one operation, not separate operations with identical data.
- Duplicate detection must handle concurrent requests safely.
What the interviewer checks: The interviewer is checking whether you understand safe retries and how to prevent duplicate effects.
Other ways it was asked
- “What does idempotency mean?”
- “What is idempotency?”
- “What is idempotency, and where is it useful in a software system?”
If a service restarts and an external service resends the same message for a 50,000-peso payment, how would you design the system so the recipient is not credited 100,000 pesos?
Asked in 6 of 942 interviews · last asked Oct 15 · Design · Senior
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I would make payment processing idempotent using a stable payment ID from the sender. In one database transaction, I would record that ID with a unique constraint and credit 50,000 pesos. A retry with the same ID would not credit again, even after a restart. I would acknowledge the message only after the transaction commits.
- Store processed payment IDs durably, not only in memory.
- The unique constraint blocks concurrent duplicates; the transaction keeps the payment record and credit together.
- Use the same payment ID across retries, not a new ID for each delivery.
- Check payment state so late events cannot repeat a credit or move a settled payment backward.
What the interviewer checks: The interviewer checks whether you can prevent duplicate credits across retries, crashes, and concurrent processing.
Other ways it was asked
- “If a service restarts and an external service resends the same message for a 50,000-peso payment, how would you prevent the recipient from receiving 100,000 pesos?”
- “If an external service resends the same 50,000-peso payment message after your service restarts, how would you prevent the recipient from receiving the payment twice?”
- “How would you design the system so that if a service restarts and an external service resends the same 50,000-peso credit message, the customer is not credited twice? How would you handle a late event indicating that the transaction is already settled or in an intermediate state?”
What is cloud computing, and what are its fundamental concepts?
Asked in 6 of 942 interviews · last asked Oct 22 · Concept · Junior
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Cloud computing means using computing resources, such as servers, storage, and software, on demand over a network. Users can get resources themselves from a shared pool and quickly increase or reduce capacity. Usage is measured, and public cloud services commonly charge based on what you use.
- Core concepts are self-service, network access, shared resources, rapid scaling, and measured usage.
- Service models include IaaS for infrastructure, PaaS for application platforms, and SaaS for ready-to-use software.
- Deployment models include public, private, and hybrid clouds.
- Security responsibilities are shared between provider and customer; the split depends on the service model.
What the interviewer checks: The interviewer checks whether you understand cloud computing beyond simply renting remote servers.
Other ways it was asked
- “What is cloud computing?”
- “What are the fundamental concepts of cloud computing?”
- “Can you explain the concept of cloud computing?”
How would you design a payment processing system?
Asked in 5 of 942 interviews · last asked Oct 9 · Design · Mid-level
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I would build a payment API backed by a durable payment store, an accounting ledger, and a payment provider. I would use idempotency keys and track each payment's state. Background workers would process provider updates and reconcile records. I would tokenize card data directly with the provider, keeping raw card data off our servers.
- Use provider idempotency keys for retries; a timeout means unknown status, not necessarily failure.
- Verify webhook signatures and handle duplicate or out-of-order events.
- Record ledger changes transactionally and reconcile them with provider records.
- Track authorization, capture, refunds, and settlement separately; protect payment data and meet applicable PCI requirements.
What the interviewer checks: The interviewer checks whether you can prevent duplicate charges, recover from partial failures, and keep money records accurate.
Other ways it was asked
- “How would you implement payment processing?”
- “How would you implement payment processing in an application?”
- “How would you design a payment system?”
What is a use case diagram?
Asked in 4 of 942 interviews · last asked Mar 27 · Concept · Junior
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A use case diagram is a UML diagram that shows what users or other systems can do with a system. It connects actors, such as customers or external services, to goals the system supports. It describes the system’s scope and external behavior, not its internal design or step-by-step flow.
- Actors are roles outside the system, not specific people.
- Use cases describe goals, such as placing an order or checking a balance.
- A system boundary separates the system’s use cases from external actors.
What the interviewer checks: The interviewer is checking whether you can describe a system’s users, goals, and scope without mixing in implementation details.
Other ways it was asked
- “Explain the use case diagram.”
- “What is a UML use case diagram?”
How do SSR, SSG, and CSR differ, and when would you use each?
Asked in 4 of 942 interviews · last asked Oct 23 · Concept · Mid-level
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SSR builds HTML on the server at request time; use it for fresh or personalized pages that need visible content quickly. SSG builds HTML ahead of time; use it for blogs or documentation that change less often. CSR builds the page in the browser with JavaScript; use it for interactive apps, such as private dashboards.
- SSR supports fresh content but adds server work and may delay the response.
- SSG is easy to cache, but content updates require rebuilding or regenerating pages.
- CSR depends on JavaScript for content, which can slow initial display and make search indexing harder.
- SSR and SSG can add client-side JavaScript for interactivity; one app can combine all three approaches.
What the interviewer checks: The interviewer checks whether you can choose a rendering approach based on freshness, search visibility, performance, and interactivity.
Other ways it was asked
- “What are client-side rendering (CSR) and server-side rendering (SSR)?”
- “What is the difference between server-side rendering (SSR), static site generation (SSG), and client-side rendering (CSR)?”
- “When would you choose static, server-side, or client-side rendering, and why?”
Why would you choose microservices, and what benefits do they offer beyond scalability?
Asked in 4 of 942 interviews · last asked Oct 7 · Concept · Senior
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I would choose microservices when separate teams need to build and release parts of a system independently. Services can also isolate failures and use different tools for different workloads. These benefits must justify harder operations, network failures, and keeping data consistent across services.
- Clear service boundaries let teams own and deploy services independently.
- Fault isolation needs timeouts and other safeguards; splitting services alone does not prevent cascading failures.
- Each service can use a language, database, or compute setup suited to its workload.
- A simpler monolith may be better when independent releases and team ownership offer little value.
What the interviewer checks: The interviewer is checking whether you can connect microservices to real needs and explain their costs beyond scaling.
Other ways it was asked
- “What are the advantages of microservices?”
- “Why do we go for microservices?”
- “What benefits can justify the trade-offs of a microservices architecture?”
What is eventual consistency?
Asked in 4 of 942 interviews · last asked Oct 15 · Concept · Mid-level
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Eventual consistency means copies of data can temporarily disagree, but will converge if updates stop and changes can reach every copy. Users may see old data or different results from different servers. Tests should allow for this delay and check that results become consistent, rather than expect every read to show the latest write.
- It does not guarantee that a read immediately shows the latest write.
- Convergence depends on updates reaching replicas and conflicts being resolved.
- Users may notice delayed profile changes, search updates, or like counts.
- Tests can retry reads within a timeout based on the system’s requirements.
What the interviewer checks: The interviewer is checking whether you understand delayed consistency and its effects on users and tests.
Other ways it was asked
- “What is eventual consistency, and what implications does it have for testing?”
- “What is eventual consistency, and where might users notice it?”
What is multitenancy?
Asked in 4 of 942 interviews · last asked Jul 16 · Concept · Junior
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Multitenancy means one software system serves multiple customers, called tenants, while keeping their data and access separate. Tenants share some infrastructure, which lowers costs and makes updates easier. It is common in software-as-a-service applications.
- A tenant is usually a customer organization, not an individual user.
- Tenants may share database tables or use separate schemas or databases.
- Every request must enforce tenant-specific access to prevent data leaks.
- Resource limits help stop one busy tenant from slowing down others.
What the interviewer checks: The interviewer checks whether you understand shared infrastructure, tenant isolation, and the trade-off between cost and isolation.
Other ways it was asked
- “What is multitenancy in application design?”
- “What is multitenancy, and what is it used for?”
- “What is multi-tenancy in a software system?”
How would you design and implement a generative AI application end to end?
Asked in 4 of 942 interviews · last asked Sep 9 · Design · Mid-level
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I would define the user task, success measures, and privacy needs first. Then I would choose a model and build the flow: authenticate requests, fetch needed context, call the model, validate outputs, and return results. I would test quality and safety before release. In production, I would monitor quality, latency, failures, and cost.
- Use retrieval for private or changing facts; enforce access rules before sending context to the model.
- Compare models and prompts on realistic test cases, including wrong answers and unsafe requests.
- Keep secrets out of prompts; treat retrieved text as untrusted and check permissions before tool actions.
- Set timeouts, retry limits, rate limits, and fallback behavior; release gradually and support rollback.
What the interviewer checks: The interviewer checks whether you can turn a model call into a secure, reliable application with measurable quality.
Other ways it was asked
- “How would you explain the flow of an end-to-end generative AI project?”
- “How would you explain a generative AI system end to end?”
- “How would you design and implement an LLM application?”
What is the difference between stateful and stateless systems?
Asked in 3 of 942 interviews · last asked Aug 5 · Concept · Junior
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A stateless system handles each request without relying on stored client session context from earlier requests. A stateful system keeps that context and uses it for later requests. Stateless services can still read and write persistent data, such as database records.
- Stateless requests carry the context needed to process them, such as an authentication token.
- Stateless servers are easier to replace or scale because requests do not depend on a specific server.
- Server-local session state may require sticky routing; shared session state requires a shared store.
- Stateful systems need a plan to preserve or recover session state after failures.
What the interviewer checks: The interviewer checks whether you distinguish session state from stored data and understand the scaling and failure trade-offs.
Other ways it was asked
- “What is the difference between stateless and stateful systems in client-server interactions and API calls?”
- “What do stateless and stateful mean, and how do they differ?”
System design fundamentals interview questions
Start with questions about requirements, design documents, UML diagrams, technology choices, and explaining trade-offs to stakeholders. 168 questions.
What do you mean by a sequence diagram?
Asked in 3 of 942 interviews · last asked Sep 28 · Concept · Junior
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A sequence diagram is a UML diagram that shows how participants, such as users, services, or objects, exchange messages during a process. Each participant has a vertical lifeline, and messages appear in order from top to bottom. It helps explain who calls whom and in what order.
- Participants appear across the top, with lifelines extending downward.
- Arrows show messages, such as requests and responses.
- It shows interaction order, not exact timing or system structure.
- It can show conditions, loops, and parallel interactions.
What the interviewer checks: The interviewer is checking whether you can describe how components interact over time using a standard diagram.
Other ways it was asked
- “What is a UML sequence diagram?”
Can you tell me about UML diagrams?
Asked in 3 of 942 interviews · last asked Jun 8 · Concept · Junior
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UML stands for Unified Modeling Language. It is a standard visual language for describing a system’s structure and behavior. Class and component diagrams show parts and relationships; sequence and activity diagrams show interactions and workflows. Teams use UML to explain designs and discuss changes before writing code.
- Structural diagrams show how a system is organized; behavioral diagrams show how it works.
- Sequence diagrams show messages between participants in order.
- Use only the diagram types and detail needed to explain the design.
- UML describes designs; it is not a development process or programming language.
What the interviewer checks: The interviewer checks whether you understand UML’s purpose and can choose a suitable diagram to explain a design.
Other ways it was asked
- “What is UML?”
- “Why are UML diagrams used, and what do they represent?”
Can you walk me through a complex system design you led and the key trade-offs you made?
Asked in 2 of 942 interviews · last asked Oct 24 · Design · Senior
Other ways it was asked
- “Can you walk me through one system design or architecture project you led and the key trade-offs you made?”
- “Tell me about a complex system you designed or owned end to end where you had to make key trade-offs.”
What is especially important when developing financial systems?
Asked in 2 of 942 interviews · last asked May 18 · Case · Senior
Other ways it was asked
- “What do you consider especially important when developing financial or banking systems?”
What is the difference between a Solution Designer and a Technical Architect?
Asked in 2 of 942 interviews · last asked Sep 30 · Concept · Mid-level
Other ways it was asked
- “What is the difference between a technical architect and a solutions architect?”
Could you give me an example of presenting an architecture trade-off or risk to a nontechnical executive or business stakeholder?
Asked in 2 of 942 interviews · last asked Oct 13 · Behavioral · Senior
Other ways it was asked
- “How would you explain the business impact of a complex architectural trade-off to a director or VP of engineering?”
How would you diagram and explain a software project's architecture?
Asked in 2 of 942 interviews · last asked Sep 2 · Design · Senior
Other ways it was asked
- “How would you describe a software project's architecture, with one or two examples?”
What does software design involve?
Asked in 2 of 942 interviews · last asked Sep 4 · Concept · Junior
Other ways it was asked
- “What is software design?”
- “Who is typically responsible for software design, and what components does the design define?”
How do you explain technical architecture and decisions to technical and non-technical clients?
Asked once · last asked Sep 14 · Behavioral · Senior
Other ways it was asked
- “How would you explain a technical architecture and its cost to a non-technical client?”
- “How do you explain technical architecture and technology choices to both technical and non-technical clients?”
How would you assess and address complexity in a Salesforce project as a solution or technical architect?
Asked once · last asked Sep 30 · Design · Senior
Other ways it was asked
- “Describe a complex Salesforce project, how you assessed its complexity, and how you addressed it as a solution or technical architect.”
- “Describe a complex Salesforce project, what made it complex, and how you resolved its architectural challenges.”
- “Describe a complex Salesforce project and explain how you addressed its challenges as a Technical Architect.”
How do you select technologies for a software project, and who should be involved in that decision?
Asked once · last asked May 14 · Scenario · Senior
Other ways it was asked
- “How do you evaluate and select technologies for a software project?”
How would you design the system and choose the technology stack for the legacy ASP.NET Web Forms application with a SQL database and RabbitMQ?
Asked once · last asked Oct 19 · Design · Senior
Other ways it was asked
- “How would you design the system and choose the technology stack for the legacy ASP.NET Web Forms application with a SQL database, RabbitMQ, device messaging, and APIs, making it multi-tenant?”
Software architecture interview questions
Explore application layers, MVC, MVVM, Clean Architecture, domain-driven design, and ways to organize code for maintainability. 237 questions.
What is domain-driven design, and when would you use it?
Asked in 3 of 942 interviews · last asked Sep 28 · Concept · Senior
Other ways it was asked
- “What is domain-driven design (DDD)?”
- “What is domain-driven design used for, what are its advantages and disadvantages, and where did it originate?”
- “What is domain-driven design (DDD), and in what situations is it particularly useful?”
How would you use MVC and hexagonal architecture, and how do they differ?
Asked in 2 of 942 interviews · last asked Sep 16 · Concept · Mid-level
Other ways it was asked
- “Why would you choose hexagonal architecture over MVC?”
- “How have you used MVC and hexagonal architecture, and how do they differ?”
- “What are the differences between MVC and hexagonal architecture, and which do you prefer?”
What is hexagonal architecture, and how does it structure an application?
Asked in 2 of 942 interviews · last asked Sep 16 · Concept · Mid-level
Other ways it was asked
- “Can you give a small example of how hexagonal architecture separates an application’s components?”
What is the foundational principle of Clean Architecture?
Asked in 2 of 942 interviews · last asked Aug 17 · Concept · Mid-level
Other ways it was asked
- “Why do we use Clean Architecture?”
How do you structure a Node.js backend project, including controllers, models, and database connections?
Asked in 2 of 942 interviews · last asked Sep 13 · Design · Mid-level
Other ways it was asked
- “How do you structure your Node.js backend?”
How would you structure a project using a monorepo or micro-frontends, and what factors would guide your approach?
Asked in 2 of 942 interviews · last asked Oct 19 · Design · Senior
Other ways it was asked
- “For a portal with shared components and customer-specific features, would you choose a monorepo or microfrontends?”
What is CQRS, and what advantages does it offer over traditional patterns?
Asked in 2 of 942 interviews · last asked Aug 31 · Concept · Mid-level
Other ways it was asked
- “What advantages does CQRS offer over traditional patterns?”
- “Can you explain CQRS?”
- “Can you explain CQRS and its implications?”
What is a component?
Asked in 2 of 942 interviews · last asked Jun 18 · Concept · Junior
How do you structure a software project?
Asked in 2 of 942 interviews · last asked Oct 22 · Concept · Junior
Other ways it was asked
- “How would you structure the development process for a software project?”
What is the difference between front-end and back-end development?
Asked in 2 of 942 interviews · last asked May 8 · Concept · Junior
Other ways it was asked
- “What is the difference between front-end and back-end development, and what is a basic feature you might build on each side of a web application?”
Can you explain the MVC and MVVM architectures?
Asked in 2 of 942 interviews · last asked Sep 30 · Concept · Mid-level
Other ways it was asked
- “Can you explain the key components of MVVM and Clean MVVM architecture?”
What are the components of ArcGIS Enterprise?
Asked once · last asked Nov 18 · Concept · Mid-level
Other ways it was asked
- “What are the components of ArcGIS Enterprise besides ArcGIS Server?”
Microservices and integration interview questions
Compare monoliths and microservices through questions about service boundaries, legacy migrations, integration patterns, and connections between enterprise systems. 167 questions.
How would you design and implement a microservices architecture integrated with Kafka?
Asked once · last asked Sep 23 · Design · Senior
Other ways it was asked
- “What microservices architecture would you choose for a system integrated with Kafka?”
How would you integrate an enterprise financial system with Office 365?
Asked once · last asked Oct 8 · Design · Senior
Other ways it was asked
- “How would you integrate an enterprise financial system with Office 365 so that actions in one system are correctly performed in the other?”
- “What challenges can arise when integrating an enterprise financial system with Office 365 so that actions are correctly performed in both systems, and how would you address them?”
How does a point-of-sale transaction flow from the register to the server?
Asked once · last asked Jun 8 · Design · Mid-level
Other ways it was asked
- “How does the database fit into the flow of a point-of-sale transaction from the register to the server?”
How would you integrate real-time FedEx shipping calculations into the Salesforce B2B Commerce checkout process?
Asked once · last asked Sep 21 · Design · Senior
Other ways it was asked
- “How would you integrate real-time shipping calculations into the Salesforce B2B Commerce checkout process?”
What are common integration patterns, and when would you use each?
Asked once · last asked Oct 1 · Concept · Senior
How would you migrate a legacy application to Spring Boot?
Asked once · last asked Oct 16 · Scenario · Senior
Given a monolithic application that takes orders, checks inventory, and generates reports, what would be your first step in migrating it to microservices, and how would you proceed?
Asked once · last asked Jan 30 · Design · Senior
How should three microservices with separate databases communicate to retrieve and share data?
Asked once · last asked Jan 31 · Design · Senior
What are the differences between monolithic systems, microservices, and REST APIs in a Java and Spring Boot backend?
Asked once · last asked Feb 6 · Concept · Senior
How would you develop integrations between web portals and a PBX using SIP trunks and WebRTC?
Asked once · last asked Feb 19 · Scenario · Mid-level
How would you approach a complex integration between HubSpot and another tool, such as Salesforce, while ensuring data consistency?
Asked once · last asked Feb 20 · Behavioral · Mid-level
Other ways it was asked
- “Tell me about a complex challenge you faced integrating HubSpot with another tool, such as Salesforce. What steps did you take to ensure data consistency?”
How do you decide whether HubSpot should be integrated with another CRM or serve as the primary source of information?
Asked once · last asked Feb 20 · Scenario · Mid-level
API design and messaging interview questions
Work through API contracts, middleware, gateways, rate limiting, queues, background jobs, WebSockets, and synchronous versus asynchronous communication. 179 questions.
What is the difference between synchronous and asynchronous communication between services?
Asked in 3 of 942 interviews · last asked Oct 23 · Concept · Mid-level
Other ways it was asked
- “How would you decide whether to use synchronous or asynchronous communication between services?”
- “What is the difference between synchronous and asynchronous services, and when would you use each?”
What is the role of an API gateway?
Asked in 3 of 942 interviews · last asked Oct 1 · Concept · Mid-level
Other ways it was asked
- “What problem does an API gateway solve?”
- “Why do we need an API gateway?”
What are WebSockets, and when would you use them?
Asked in 2 of 942 interviews · last asked Mar 5 · Concept · Mid-level
Other ways it was asked
- “What are WebSockets?”
How would you decide whether to use Kafka or RabbitMQ for an application?
Asked in 2 of 942 interviews · last asked Sep 21 · Scenario · Mid-level
Other ways it was asked
- “When would you choose Kafka over Amazon SQS or BullMQ for a distributed application?”
How can a REST API be stateless if a request to retrieve a resource depends on an earlier request that created it?
Asked once · last asked Jan 29 · Concept · Mid-level
Other ways it was asked
- “In a REST API, is creating a resource in one request and retrieving it in a later request considered stateful or stateless?”
What problems could arise if a notification system sends a batch only when the queue contains more than 10 messages?
Asked once · last asked Mar 31 · Scenario · Mid-level
Other ways it was asked
- “What problem could occur if a notification system waits for a queue to exceed 10 messages before sending, when it receives only two messages per day?”
How would you run dynamic background jobs as Kubernetes Jobs or Rails processes, consume work from a queue, and handle long-running tasks?
Asked once · last asked Jul 24 · Design · Senior
Other ways it was asked
- “How do dynamic background jobs run as Kubernetes Jobs or Rails processes, pick up work from a queue, and handle long-running tasks?”
What are the time and space complexities of the `allow` operation in a rolling-window rate limiter?
Asked once · last asked Sep 6 · Concept · Mid-level
Other ways it was asked
- “Why is the `allow` operation in a rolling-window rate limiter amortized O(1), and what are its time and space complexities?”
How would you design an API to handle millions of records?
Asked once · last asked Sep 30 · Design · Senior
Other ways it was asked
- “How would you design pagination for an API that needs to handle millions of records?”
What data structure ensures fairness in checkout processing, and how do we prevent the payment system from overloading?
Asked once · last asked Oct 6 · Design · Mid-level
Other ways it was asked
- “What data structure would you use to ensure fair first-come-first-served processing for checkout payments while preventing the payment system from being overloaded?”
Why use a message queue or broker instead of making an HTTP call for every message?
Asked once · last asked Jan 28 · Concept · Mid-level
How would you render HTML for a form retrieved from an external API when the API requires a client secret that must not be exposed to the front end?
Asked once · last asked Feb 9 · Scenario · Mid-level
Database and data pipeline system design interview questions
Test your understanding of storage choices, data models, caching, replication, sharding, consistency, transactions, batch processing, and streaming. 267 questions.
What is database replication?
Asked in 2 of 942 interviews · last asked Feb 22 · Concept · Junior
Other ways it was asked
- “What is database replication, and what is it used for?”
- “How does database replication work, and what is it used for?”
- “How does database replication work?”
How do you design and implement batch processing?
Asked in 2 of 942 interviews · last asked Jun 10 · Concept · Mid-level
Other ways it was asked
- “What do you consider when designing and developing batch processing systems?”
How does the Raft consensus algorithm work, and how would you use it?
Asked in 2 of 942 interviews · last asked Aug 21 · Concept · Senior
Other ways it was asked
- “What is the Raft consensus algorithm, and how does it work?”
What are distributed transactions, and when would you use them?
Asked in 2 of 942 interviews · last asked Aug 19 · Concept · Mid-level
Other ways it was asked
- “What are some alternatives to distributed transactions?”
What is sharding?
Asked in 2 of 942 interviews · last asked Mar 27 · Concept · Junior
Other ways it was asked
- “What is database sharding?”
How does data replication work in the cloud?
Asked in 2 of 942 interviews · last asked Dec 4 · Concept · Mid-level
Other ways it was asked
- “What are the types of data replication in cloud computing?”
What architecture and tools would you use in an SAP Datasphere project?
Asked in 2 of 942 interviews · last asked Oct 6 · Design · Senior
Other ways it was asked
- “How do you consume data in SAP Datasphere, and what does the architecture look like?”
How would you balance user experience against consistency in a payment-card system?
Asked once · last asked Mar 16 · Scenario · Senior
Other ways it was asked
- “How would you handle a conflict between a consistency requirement and a better user experience in a payment-card system?”
When writing data that must appear in both a cache and a database, which should receive the initial write?
Asked once · last asked Mar 16 · Design · Senior
Other ways it was asked
- “When writing data to both a cache and a database, which should receive the initial write?”
How would you handle atomicity when updating both a cache and a database?
Asked once · last asked Mar 16 · Design · Senior
Other ways it was asked
- “How can you make an operation that updates both a cache and a database atomic?”
For a system like Instagram, would you choose a NoSQL or relational database? Give specific examples and explain why.
Asked once · last asked May 11 · Design · Senior
Other ways it was asked
- “If you chose a NoSQL database for a system like Instagram, which one would you select, such as MongoDB, and why?”
How would you approach designing an end-to-end system for handling high-volume real-time event data like user actions or messages coming in rapidly?
Asked once · last asked Jul 22 · Design · Senior
Other ways it was asked
- “How would you approach end-to-end system design for handling high volume of basic event data like user actions or messages coming in rapidly? Walk through the key components you'd consider.”
- “How would you architect a system that needs to handle a high volume of real-time events to ensure scalability and reliability?”
Scalability and reliability interview questions
Check how you would scale a system, balance traffic, reduce latency, handle failures, manage retries, and recover. 353 questions.
What are Veritas clusters?
Asked in 3 of 942 interviews · last asked Dec 4 · Concept · Mid-level
Other ways it was asked
- “What is a Veritas cluster?”
How would you design an application and its services to scale as the user base grows?
Asked in 3 of 942 interviews · last asked Sep 21 · Design · Senior
Other ways it was asked
- “What does application scalability mean, and how would you design an application to scale?”
- “How would you design an application to scale?”
- “If you wanted to scale the application to 100,000 users, how would you ensure the architecture and services support scalability?”
What is a cascading failure?
Asked in 2 of 942 interviews · last asked Oct 6 · Concept · Mid-level
Other ways it was asked
- “How can you solve cascading failures?”
How does the circuit breaker pattern work?
Asked in 2 of 942 interviews · last asked Oct 9 · Concept · Senior
Other ways it was asked
- “Can you explain the circuit breaker pattern?”
How would you prevent duplicate SMS messages when processing repeated requests?
Asked in 2 of 942 interviews · last asked Jul 27 · Concept · Senior
Other ways it was asked
- “How would you prevent duplicate SMS messages from being sent?”
How would you design idempotency for a POS/payments endpoint, including the database schema and API contract, so retries don't create duplicate charges?
Asked in 2 of 942 interviews · last asked Oct 22 · Design · Senior
Other ways it was asked
- “In a high-throughput REST API, how would you implement idempotency for POS or payments so retries don't double-charge?”
How would you prepare an ecommerce startup's architecture for a high-traffic event like Black Friday?
Asked in 2 of 942 interviews · last asked Oct 23 · Scenario · Senior
Other ways it was asked
- “How would you prepare an ecommerce platform to support 2,000,000 users or handle Black Friday traffic?”
If a downstream service is slow or unavailable, how would you prevent your application from failing?
Asked in 2 of 942 interviews · last asked Oct 23 · Scenario · Senior
Other ways it was asked
- “How would you protect a mobile app when a downstream service becomes slow but does not fail?”
What is a load balancer?
Asked in 2 of 942 interviews · last asked Feb 22 · Concept · Junior
What is redundancy?
Asked in 2 of 942 interviews · last asked Aug 14 · Concept · Junior
Other ways it was asked
- “What is data redundancy?”
How would you design microservices to handle 2.5 million requests while keeping a changing dataset up to date across services?
Asked once · last asked Aug 22 · Design · Senior
Other ways it was asked
- “How would you design microservices to handle 2.5 million requests?”
- “How would you design the software infrastructure for microservices that use a shared dataset and handle 2.5 million requests per second?”
- “How would you design the software infrastructure for microservices that process a shared dataset and handle 2.5 million requests per second?”
Can you explain horizontal scaling and how you would implement it?
Asked once · last asked Mar 3 · Concept · Mid-level
Cloud architecture and multitenancy interview questions
Cloud questions cover service choices, deployment, infrastructure sizing, multi-region availability, tenant isolation, security, and data residency. 233 questions.
How would you design a multi-tenant ERP architecture?
Asked in 3 of 942 interviews · last asked Oct 7 · Design · Senior
Other ways it was asked
- “How would you design a multi-tenant architecture?”
- “Explain your multi-tenant ERP architecture.”
How would you enforce tenant isolation and prevent cross-tenant data access in a multitenant application?
Asked in 3 of 942 interviews · last asked Sep 1 · Scenario · Senior
Other ways it was asked
- “How would you prevent one customer's data from being exposed to another customer in a multitenant system?”
- “How would you handle schema isolation and security in a multitenant SaaS application?”
- “How would you implement middleware for tenant isolation in a multitenant SaaS application?”
How would you design a highly available data platform on AWS?
Asked in 2 of 942 interviews · last asked Aug 31 · Design · Senior
Other ways it was asked
- “How do you design a highly available application in AWS?”
What are the trade-offs between serverless and a regular server architecture, and when should you use each?
Asked in 2 of 942 interviews · last asked Jul 28 · Design · Mid-level
Other ways it was asked
- “Given the benefits and shifts you've mentioned with serverless computing, how do you decide when to use a serverless approach versus a traditional server-based architecture in your projects?”
When would you choose AWS Lambda over an EC2 instance for a compute task?
Asked in 2 of 942 interviews · last asked Oct 23 · Concept · Senior
Other ways it was asked
- “When would you choose Lambda instead of an EC2 instance?”
How would you design a multi-region AWS architecture to provide high availability and security for an application?
Asked in 2 of 942 interviews · last asked Sep 30 · Design · Senior
Other ways it was asked
- “How would you design a simple cross-region application architecture on AWS?”
How would you organize a multitenant database, and when would you use shared or separate tables?
Asked in 2 of 942 interviews · last asked Oct 2 · Design · Senior
Other ways it was asked
- “How would you manage tenant data in a multi-tenant application?”
- “How would you manage the database for a multi-tenant application?”
- “Which database would you choose for a new multi-tenant project, and how would you implement the multi-tenancy?”
What is the difference between PaaS and SaaS?
Asked in 2 of 942 interviews · last asked May 6 · Concept · Junior
Other ways it was asked
- “What is the difference between SaaS and PaaS?”
Which AWS services would you consider when designing a batch-processing system?
Asked once · last asked Mar 9 · Design · Mid-level
Other ways it was asked
- “How would you design an AWS architecture for batch processing, and what principles would guide your design?”
- “What factors do you consider when designing an AWS batch-processing environment?”
What factors can motivate moving Apache NiFi from on-premises infrastructure to the cloud, and what challenges might arise?
Asked once · last asked Feb 6 · Scenario · Mid-level
What managed SQL database services are available in AWS, GCP, and Azure, and how do they compare with on-premises SQL Server?
Asked once · last asked Feb 7 · Concept · Mid-level
What is Sitecore Experience Edge, and how does it differ from a Sitecore Content Delivery server?
Asked once · last asked Feb 9 · Concept · Mid-level
Other ways it was asked
- “How does Sitecore Experience Edge deliver content faster than a Sitecore Content Delivery server?”
AI system design interview questions
AI design questions cover RAG, LLM applications, agents, chatbots, voice systems, model choices, evaluation, privacy, and production trade-offs. 274 questions.
When would you choose a fixed workflow, a single agent, or a multi-agent system?
Asked in 3 of 942 interviews · last asked Aug 18 · Concept · Senior
Other ways it was asked
- “Why might you build a fixed workflow when agent technology is available?”
- “When would you use a fixed workflow, a single agent, or a multi-agent system?”
- “Why did you use the multi-agent architecture instead of just using a single LLM call?”
How would you reduce latency in a voice-based AI platform?
Asked in 2 of 942 interviews · last asked Sep 24 · Scenario · Senior
Other ways it was asked
- “How would you reduce latency in an AI system?”
What steps would you take to take a generative AI project from scratch to production?
Asked in 2 of 942 interviews · last asked Jul 14 · Design · Senior
Other ways it was asked
- “How would you take a generative AI application from initial design through production deployment?”
A long-term care pharmacy software company has about 200 facilities using its software and handles around 400 support tickets a day, with 40% covering repeated questions. Its agents have trouble finding answers in the documentation. Can AI help, and how would you approach this?
Asked in 2 of 942 interviews · last asked May 13 · Design · Junior
Other ways it was asked
- “How would you design an AI system to help a long-term-care pharmacy support team find answers in its documentation faster, serving about 200 facilities and handling 400 tickets a day, with roughly 40% repetitive tickets?”
How would you design the high-level architecture of an AI agent?
Asked in 2 of 942 interviews · last asked Jul 16 · Design · Mid-level
Other ways it was asked
- “How would you design an AI agent, including its system architecture and tool choices?”
How would you design the architecture of an AI system?
Asked in 2 of 942 interviews · last asked Jul 16 · Design · Senior
Other ways it was asked
- “Tell me about an AI system you built and explain its architecture.”
- “Describe an AI solution you built: what model did you choose, why did you choose it, and what was the architecture?”
How would you build an MCP server, and what components would it include?
Asked in 2 of 942 interviews · last asked Sep 8 · Design · Mid-level
Other ways it was asked
- “How would you architect an application using an MCP server, including the client-side components?”
- “How would you design an MCP server for an application, and what three tools or capabilities would it expose?”
How would you design a production multi-agent system end to end?
Asked in 2 of 942 interviews · last asked Oct 7 · Design · Senior
Other ways it was asked
- “How would you orchestrate a multi-agent system?”
Can AI systems be built using open-source or closed-source models, and how do those approaches differ?
Asked in 2 of 942 interviews · last asked Oct 13 · Concept · Junior
Other ways it was asked
- “What is the difference between open-source and closed-source AI models?”
How would you design an AI system to determine whether a site unit is ready for site acceptance testing, identify blockers, and provide the right contact?
Asked once · last asked Sep 29 · Design · Senior
Other ways it was asked
- “How would you design an AI system to assess a site unit's readiness for site acceptance testing?”
- “How would you design a real-time AI system to determine whether a site unit is ready for site acceptance testing, identify blockers, and provide the right contact?”
- “How would you build an AI system for a field engineer to check whether a site unit is ready for site acceptance testing?”
What components would an agent-based system need to convert test scenarios into Playwright tests?
Asked once · last asked Oct 8 · Design · Senior
Other ways it was asked
- “How would you build an agent to convert test scenarios into Playwright tests?”
- “How long might it take to build an agent that converts test scenarios into Playwright tests?”
How would you design an AI system to enhance customer support?
Asked once · last asked Jun 22 · Design · Mid-level
Other ways it was asked
- “Which technique would you use to build an AI system that enhances customer support?”
System design interview case study questions
Try end-to-end design questions for payments, booking, commerce, social media, streaming, file storage, tracking, and other business applications. 185 questions.
How would you design a video streaming service like YouTube?
Asked in 2 of 942 interviews · last asked Jul 25 · Design · Senior
Other ways it was asked
- “What are the key components of a video streaming service like YouTube?”
- “How would you design a streaming platform?”
How would you design a cinema ticket-booking system?
Asked in 2 of 942 interviews · last asked Oct 7 · Design · Mid-level
Other ways it was asked
- “How would you design the architecture for an event ticket booking system?”
Can you design an Instagram-like system?
Asked in 2 of 942 interviews · last asked Sep 29 · Design · Senior
Other ways it was asked
- “How would you design a system like Instagram?”
How would you approach designing and building a transactional platform for a fintech business?
Asked once · last asked Apr 11 · Design · Mid-level
Other ways it was asked
- “How would you estimate the cost of building a transactional platform for a fintech business?”
How should the system handle a core system confirming a reservation at a different price from the accepted offer?
Asked once · last asked Sep 30 · Scenario · Mid-level
How would you design and implement a wish-list feature for an e-commerce application, considering data storage, the user interface, and scalability?
Asked once · last asked Mar 31 · Design · Mid-level
Other ways it was asked
- “What challenges might arise when developing a wish-list feature for an e-commerce application, and how would you address them?”
How would you handle two files with the same name being uploaded?
Asked once · last asked Jun 25 · Scenario · Mid-level
Other ways it was asked
- “How would you handle two users uploading files with the same name?”
How would you make a drug-alias lookup system production-ready?
Asked once · last asked Jul 24 · Design · Senior
Other ways it was asked
- “If you had limited time to make a drug-alias lookup system production-ready, what would you fix first?”
How would you design an electronic voting system so the final result accurately reflects the votes cast, each vote remains confidential, no partial results are accessible, and only authorized voters can vote once?
Asked once · last asked Dec 4 · Design · Senior
Other ways it was asked
- “How would you ensure the confidentiality of votes in an electronic voting system?”
In a chunked file upload system, does validation run on the complete file after assembly or on each chunk as it arrives?
Asked once · last asked Aug 24 · Design · Senior
If you were asked to implement an attendance system for a college, what would you do?
Asked once · last asked Sep 10 · Design · Mid-level
Other ways it was asked
- “If a college asked you to build an attendance system, what would you consider and how would you implement it?”
How would you approach screen analytics to determine what an agent is doing and how much time they spend in applications such as Outlook or Facebook?
Asked once · last asked Oct 7 · Design · Senior
Other ways it was asked
- “How would you use screen analytics to measure an agent's activity, time spent in applications, and metrics such as emails sent?”
All 185 System design interview case study questions questions
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How this list is made
Every question here was asked by a real interviewer in a real job interview that a candidate ran MeetAssist in. After the call, the interviewer's questions are pulled from the transcript. Practice sessions, tests, exams and anything that was not a job interview are dropped.
Questions are rewritten so they make sense on their own: names of people, employers and clients are removed, and speech-to-text mistakes are fixed. Small talk, logistics and questions about one candidate's own résumé are left out. Rephrasings of the same question are merged, and the count is the number of different interviews it came up in.
The interviews come from candidates who use MeetAssist, so they lean towards software, data and AI roles: the shares describe these interviews, not every System Design interview. Answers to the most asked questions are written and checked by an editor; a "common mistake" is shown only when reviews of real answers in these interviews show it, with the count.
942 interviews, 495 candidates, Oct 2025 to Oct 2026. Updated every month with new interviews.
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