All 179 questions
How would you design a rate limiter for a public API?
Asked in 9 of 942 interviews · last asked Oct 21 · Design · Senior
Show answer
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
Show answer
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 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
Besides authorization, roles, and permissions, what other use cases are appropriate for middleware?
Asked once · last asked Feb 10 · Concept · Mid-level
How would you protect a ticket-booking website from users repeatedly refreshing the page to check availability and potentially abusing the system?
Asked once · last asked Feb 11 · Scenario · Mid-level
Where would you implement rate limiting—within the API endpoints or in another component?
Asked once · last asked Feb 11 · Design · Mid-level
What rate-limiting patterns are available, and how can they be set up?
Asked once · last asked Feb 11 · Concept · Senior
How would you use socket integration to support real-time messaging in a chat application?
Asked once · last asked Feb 18 · Concept · Mid-level
How can a payment service notify a delivery service that an order has been paid so delivery can begin?
Asked once · last asked Feb 22 · Scenario · Mid-level
How would you implement pagination that loads the next items as the user scrolls?
Asked once · last asked Feb 27 · Scenario · Mid-level
If you were designing the client-server protocol yourself, for example as a browser developer, how would you make sure the server returns the website corresponding to the domain the user enters?
Asked once · last asked Mar 2 · Concept · Mid-level
If an AI agent takes one minute to generate a response, can an API endpoint with a shorter response-time limit still deliver it?
Asked once · last asked Mar 4 · Scenario · Mid-level
How would you design a rate limiter for an API allowing 50 requests per second per user across multiple stateless application servers? What components and data stores would you use, and how would you enforce consistency?
Asked once · last asked Mar 16 · Design · Senior
How would you implement a distributed rate limiter using Redis or another store, and what exact atomic operations would you rely on to avoid race conditions?
Asked once · last asked Mar 16 · Design · Senior
How would you decide whether the API gateway should call a third-party card vendor synchronously?
Asked once · last asked Mar 16 · Design · Senior
How do you design a distributed task queue for background jobs?
Asked once · last asked Mar 17 · Design · Senior
In an asynchronous order workflow, when should the customer be told that an order has been purchased?
Asked once · last asked Mar 19 · Design · Senior
How would you handle a third-party API's 429 Too Many Requests responses in PHP, including immediate backoff, respecting Retry-After, and system-wide throttling or queuing to prevent repeated rate-limit errors?
Asked once · last asked Mar 26 · Scenario · Senior
Other ways it was asked
- “When a third-party API rate-limits you, how do you handle 429 Too Many Requests in PHP? What do you do immediately for that request, such as backing off and respecting Retry-After, and what system-wide throttling or queuing do you implement to prevent repeated 429 responses?”
How would you modify a notification system to batch messages instead of sending them immediately whenever dispatch is called?
Asked once · last asked Mar 31 · Design · Mid-level
In a batched notification system, how would you decide when to send the queued messages?
Asked once · last asked Mar 31 · Scenario · Mid-level
Can you tell me the difference between a command and an event that might be fired?
Asked once · last asked Apr 2 · Concept · Mid-level
Can a command have multiple subscribers, or is there just a single subscriber?
Asked once · last asked Apr 2 · Concept · Mid-level
When exposing a service for external consumers, how would you choose between providing API endpoints and publishing a NuGet package?
Asked once · last asked Apr 2 · Design · Mid-level
When would you use Node.js to develop APIs versus handle background processing?
Asked once · last asked Apr 3 · Concept · Mid-level
What are short polling and long polling, and how do they differ?
Asked once · last asked Apr 17 · Concept · Mid-level
When a front end calls a back-end API that triggers a long-running job, how would you design the API contract so the UI can reliably track progress, handle retries safely, and avoid duplicate work?
Asked once · last asked Apr 17 · Design · Senior
How can rate limits on metasearch platforms affect an integration, and how would you handle them?
Asked once · last asked Apr 27 · Scenario · Mid-level
Why would the APIs read data from Pub/Sub instead of a database?
Asked once · last asked Apr 30 · Concept · Senior
How would you implement queue prioritization and fairness so interactive requests aren't starved by large AI training jobs, and what metrics would you watch to validate it?
Asked once · last asked May 5 · Design · Senior
How would you design a simple back-end API to handle user login requests while ensuring scalability and security? Outline the key components and design decisions you would make.
Asked once · last asked May 8 · Design · Mid-level
Where does an API gateway fit, and is it more suitable for monolithic or microservice-based systems?
Asked once · last asked May 22 · Concept · Senior
How would you handle a consumer that cannot be updated quickly but must keep working during a notification payload schema migration?
Asked once · last asked May 23 · Scenario · Senior
How would you prevent abuse, such as notification spamming, while keeping the system responsive for legitimate traffic?
Asked once · last asked May 23 · Design · Senior
How would you structure the back-end API for notifications, including endpoints and data shapes, to support both real-time and paginated access?
Asked once · last asked May 23 · Design · Senior
What is the difference between synchronous and asynchronous integrations, and what technical approaches could be used for each?
Asked once · last asked Jun 9 · Concept · Mid-level
When you're working on a project, how would you decide whether to use XML or JSON serialization? What factors would influence your choice?
Asked once · last asked Jun 16 · Scenario · Mid-level
How would you design the flow from publishing an event to consuming it with Azure Service Bus, including consumer counts and partitions?
Asked once · last asked Jun 18 · Design · Senior
What does API-first mean, and how does the approach apply when working with existing products that already have APIs?
Asked once · last asked Jun 18 · Concept · Senior
How can a sliding-window mechanism be implemented with Axway Secure Transport, and is it built in or custom-developed?
Asked once · last asked Jun 18 · Concept · Senior
How would you design an event-driven solution, including its components and actors, and how would information flow through it?
Asked once · last asked Jun 24 · Design · Senior
In your experience, what are some key considerations when designing a back end system to support real-time communication features?
Asked once · last asked Jul 16 · Design · Senior
Is middleware used only for authentication?
Asked once · last asked Jul 16 · Concept · Junior
How would you send email to one million users in Laravel reliably, without the process being interrupted?
Asked once · last asked Jul 16 · Scenario · Senior
How can we implement domain-based routing in our application?
Asked once · last asked Jul 16 · Tooling · Senior
When designing an interface between two systems, what factors determine whether it should be synchronous or asynchronous, and which tools and protocols would you use?
Asked once · last asked Jul 16 · Design · Senior
What security and scalability best practices do you follow when designing an API for another system to call?
Asked once · last asked Jul 16 · Design · Senior
What is the role or function of the Web Adaptor?
Asked once · last asked Nov 18 · Concept · Mid-level
Walk through how you would design a scalable FastAPI backend service for triggering and orchestrating workflows.
Asked once · last asked Jul 16 · Design · Mid-level
How would you add a concurrency limit to an integration platform to avoid overwhelming downstream systems?
Asked once · last asked Jul 16 · Design · Senior
When you don't know the image dimensions upfront and want to avoid a full download, how do you design the API/client flow to get dimensions efficiently and still handle failures or slow networks?
Asked once · last asked Jul 20 · Design · Senior
Create an endpoint for a global rate limiter service that accepts a request containing a user ID, name, and timestamp.
Asked once · last asked Jul 22 · Write code · Senior
How would you handle concurrent requests in the rate limiter?
Asked once · last asked Jul 22 · Scenario · Senior
Suppose you need to design a task scheduling system where jobs run at specific times and need to scale. How would you design it?
Asked once · last asked Jul 22 · Design · Senior
In a Node.js system, if you need to handle large file uploads without blocking the server, how would you design that process?
Asked once · last asked Jul 23 · Design · Mid-level
What is the difference between server-side and client-side API calls?
Asked once · last asked Jul 28 · Concept · Mid-level
Would Kafka replace Redis in a chat system design?
Asked once · last asked Jul 28 · Design · Senior
If a recipient is offline when a message is sent, how would you handle delivery?
Asked once · last asked Jul 28 · Scenario · Senior
How do APIs retrieve data, and how do they fit into database design and connecting a frontend to a backend?
Asked once · last asked Aug 3 · Concept · Junior
How does the order in which you register middleware components affect how requests are handled? Can you give an example of why order matters?
Asked once · last asked Aug 5 · Scenario · Mid-level
What are the core architectural differences between REST APIs using JSON and gRPC services?
Asked once · last asked Aug 5 · Concept · Mid-level
What API schema and flow would support requesting a ride, pickup, and drop-off?
Asked once · last asked Aug 10 · Design · Mid-level
Why might you place a durable queue between a user-facing API and a background worker?
Asked once · last asked Aug 10 · Concept · Mid-level
Walk me through the architecture of the webhook ingestion and fulfillment state machine end to end — from the incoming webhook to the final side effects.
Asked once · last asked Aug 11 · Design · Senior
Should label requests requiring immediate availability remain synchronous, or could they also use an eventually consistent approach?
Asked once · last asked Aug 11 · Design · Senior
How would you extend a synchronous label purchase system to support asynchronous label generation and URL delivery while keeping the immediate-label path unchanged?
Asked once · last asked Aug 11 · Design · Senior
Where should a user notification endpoint live when platform clients need to notify their own end users about label status?
Asked once · last asked Aug 11 · Design · Senior
How would you support customers who cannot use webhooks and need to call an API to get a response?
Asked once · last asked Aug 11 · Design · Senior
How would you handle a task that takes five minutes to complete in a web application?
Asked once · last asked Aug 13 · Scenario · Mid-level
For a PDF-processing task, would you use a background task instead of processing the PDF during the request?
Asked once · last asked Aug 13 · Scenario · Mid-level
What questions would you ask to clarify the requirements for a rate limiter?
Asked once · last asked Aug 19 · Design · Senior
How would you design a rate limiter that enforces per-user and per-IP limits for tens of millions of daily active users?
Asked once · last asked Aug 19 · Design · Senior
Why would you choose the token bucket algorithm over other rate-limiting algorithms?
Asked once · last asked Aug 19 · Concept · Senior
Other ways it was asked
- “Why would you choose only the token bucket algorithm for a rate limiter?”
How would you diagram the workflow and system connections for a rate-limiting approach?
Asked once · last asked Aug 19 · Design · Senior
How would you design a proxy between an application and a database to forward requests and responses?
Asked once · last asked Aug 21 · Design · Senior
Design a low-latency rate limiter for a global API platform with multi-tenant per-customer quotas, multi-region active-active, and p99 latency under 10 milliseconds.
Asked once · last asked Aug 24 · Design · Senior
How would you enforce strict global tenant quotas without regional drift while maintaining low latency in an active-active, multi-region rate limiter?
Asked once · last asked Aug 24 · Design · Senior
Draw the high-level data flow for a global rate limiter involving a client, edge, quota check, and authoritative store.
Asked once · last asked Aug 24 · Design · Senior
How do you handle WebSocket connections for an online game, especially with concurrent users and reconnects?
Asked once · last asked Aug 26 · Design · Senior
Other ways it was asked
- “How would you use WebSockets to reconnect clients, rehydrate game state, and manage channel subscriptions in an online game?”
How would you handle multiple game sessions and separate socket channels?
Asked once · last asked Aug 26 · Design · Mid-level
How would you coordinate a webhook payload, a database write, and a queue when processing an incoming webhook?
Asked once · last asked Aug 26 · Design · Senior
How can Django be used to build asynchronous, real-time applications, what best practices should you follow, and when would you recommend this approach?
Asked once · last asked Aug 28 · Design · Mid-level
How would you design a simple event-driven background job for something like sending emails or processing long tasks? Just the high-level components.
Asked once · last asked Sep 1 · Design · Senior
How would you determine when all child jobs in a CSV import have completed and mark the overall import as complete?
Asked once · last asked Sep 2 · Design · Senior
How should the sub-jobs be structured to handle processing, validation, and insertion for different file types?
Asked once · last asked Sep 2 · Design · Senior
How do we handle long-running API calls for each row during batch processing without stalling the system?
Asked once · last asked Sep 2 · Design · Senior
Should a master job enqueue batches of 100 rows, with each batch then creating another 100 jobs, one per row?
Asked once · last asked Sep 2 · Design · Senior
How would you update a CSV import's progress feedback to show users what is happening during a long-running process?
Asked once · last asked Sep 2 · Design · Mid-level
How would you design a document-processing workflow in which requests are queued and workers process them?
Asked once · last asked Sep 3 · Design · Mid-level
How would you design an API and choose a queue for a document-processing workflow handled by background workers?
Asked once · last asked Sep 3 · Design · Mid-level
How would you design a workflow for processing a document when multiple types of jobs need to be performed on it?
Asked once · last asked Sep 3 · Design · Mid-level
How would you design a pattern that supports multiple worker types processing the same queued document job?
Asked once · last asked Sep 3 · Design · Mid-level
Design a data structure for a rolling window rate limiter.
Asked once · last asked Sep 6 · Write code · Senior
What approach would you use for a rolling-window rate limiter, and what trade-offs would you consider?
Asked once · last asked Sep 6 · Design · Senior
How does a 10 GB file get uploaded to the backend?
Asked once · last asked Sep 8 · Design · Mid-level
What API endpoints do you need to create a URL shortener, specifically how do you generate the shortened URL?
Asked once · last asked Sep 8 · Design · Mid-level
What potential issues would you look for in a URL shortener API design?
Asked once · last asked Sep 8 · Scenario · Mid-level
Design a rate limiter that allows each user to make at most 100 requests per minute. Can it support multiple servers, handle Redis outages and race conditions, and choose between fixed and sliding windows?
Asked once · last asked Sep 9 · Design · Senior
How would you handle long-running operations, such as large exports, without blocking requests?
Asked once · last asked Sep 9 · Scenario · Senior
How would you chunk a large file for upload, and how would you choose the chunk size?
Asked once · last asked Sep 9 · Scenario · Mid-level
How would you notify the front end when an asynchronous chatbot job is complete?
Asked once · last asked Sep 10 · Design · Mid-level
How do front-end and back-end systems integrate, and how would you test APIs with Postman?
Asked once · last asked Sep 10 · Tooling · Mid-level
After an asynchronous request is accepted, how can the user retrieve the results?
Asked once · last asked Sep 10 · Design · Senior
How can a user determine that asynchronous processing is complete and the results have been saved to Amazon S3?
Asked once · last asked Sep 10 · Design · Senior
How would you design an event-driven system, including its components and how they communicate?
Asked once · last asked Sep 10 · Behavioral · Senior
Other ways it was asked
- “Describe an event-driven system you designed, including its components and how they communicate.”
Why would you use WebSockets instead of a REST API?
Asked once · last asked Sep 13 · Concept · Mid-level
How can Protocol Buffers be used to process or transport files produced by a C# system?
Asked once · last asked Sep 15 · Concept · Mid-level
How would you design a Node.js backend with GraphQL for a product catalog application?
Asked once · last asked Sep 17 · Design · Senior
If product, customer, and order data are owned by separate microservices, how would you design a federated GraphQL architecture to expose them through a unified API while keeping service independence and performance?
Asked once · last asked Sep 17 · Design · Senior
How would you design APIs in a full-stack application to scale under increased load?
Asked once · last asked Sep 17 · Design · Senior
What parts of a data synchronization process would you make asynchronous, and how would you implement them?
Asked once · last asked Sep 18 · Scenario · Senior
If an external API suddenly cuts its rate limit in half, what would you change first in an export process?
Asked once · last asked Sep 18 · Scenario · Senior
How would you connect the frontend, backend, and services in a chat application that handles text, images, and video, and choose between REST, SignalR, and Service Bus?
Asked once · last asked Sep 18 · Design · Senior
How would you choose between a REST API and SignalR for a chat application, and why?
Asked once · last asked Sep 18 · Design · Mid-level
How would you route a request through Azure Service Bus when the system needs to send a request and receive a response?
Asked once · last asked Sep 18 · Design · Senior
How would you divide queues or topics for different image types or business scenarios?
Asked once · last asked Sep 18 · Design · Senior
What could you use instead of Kafka, and how would you know which option is better for your system than other queues?
Asked once · last asked Sep 18 · Design · Mid-level
Why would you use a message queue, and what factors would lead you to choose Kafka?
Asked once · last asked Sep 18 · Design · Mid-level
How would you route traffic from a frontend to an API gateway, and when would you put a load balancer in between?
Asked once · last asked Sep 21 · Design · Mid-level
What is a reverse proxy and why is it important in web applications?
Asked once · last asked Sep 21 · Concept · Mid-level
How do you handle asynchronous operations and timeouts between user calls through an MCP server and database responses?
Asked once · last asked Sep 21 · Scenario · Senior
What edge API contract would you expose for a career search flow, and how would you validate requests and responses on both sides?
Asked once · last asked Sep 22 · Design · Mid-level
Other ways it was asked
- “What API contract would you expose for a search flow, and how would you validate requests and responses on both sides?”
For a search request, how would you trace the server-side path through edge or gateway services, and what communication patterns would the services use?
Asked once · last asked Sep 22 · Design · Senior
How would you design an integration layer between a mobile app and a backend?
Asked once · last asked Sep 23 · Design · Mid-level
How would you design or optimize a challenging RESTful API to address performance and scaling concerns?
Asked once · last asked Sep 23 · Behavioral · Mid-level
Other ways it was asked
- “Can you share an example of a challenging RESTful API you designed or optimized, and how you handled performance or scaling concerns there?”
How can queues improve performance in a highly scalable, complex application?
Asked once · last asked Sep 23 · Design · Senior
How would you implement sending an email template to 1,000 leads every Monday?
Asked once · last asked Sep 28 · Scenario · Mid-level
Other ways it was asked
- “How would you handle sending an email and a WhatsApp message to 1,000 leads at the same time every Monday?”
Why would you use multiple named queues instead of a single queue in a background job system?
Asked once · last asked Sep 28 · Concept · Mid-level
How would you update a dashboard in real time when webhooks are received?
Asked once · last asked Oct 1 · Design · Mid-level
How would you build a rate limiter shared across multiple API instances?
Asked once · last asked Oct 5 · Design · Mid-level
How would you address a frontend that sends requests every second instead of every five minutes, making backend operations too costly?
Asked once · last asked Oct 6 · Scenario · Senior
How can a server control requests when a frontend sends them too frequently?
Asked once · last asked Oct 6 · Scenario · Senior
How would you design an API for uploading and storing photos?
Asked once · last asked Oct 7 · Design · Mid-level
Other ways it was asked
- “How would you store uploaded photos as files, and how would the API handle them?”
What should a web application do when a WebSocket connection disconnects?
Asked once · last asked Oct 8 · Scenario · Mid-level
What identifier would you use to associate a calculation event with its source?
Asked once · last asked Oct 9 · Concept · Mid-level
Which Python technology or library would you choose first to build an internal API that integrates existing systems and supports bidirectional communication?
Asked once · last asked Oct 13 · Scenario · Mid-level
How do message queues, Redis, and dead-letter queues (DLQs) support distributed systems?
Asked once · last asked Oct 15 · Concept · Senior
How would you implement a fire-and-forget mechanism?
Asked once · last asked Oct 16 · Scenario · Senior
How would you expose a microservice so that 10 to 15 different consumers can use it?
Asked once · last asked Oct 16 · Design · Mid-level
When would you recommend using an event bus in an application?
Asked once · last asked Oct 19 · Design · Senior
Other ways it was asked
- “Would you recommend using an event bus for this application?”
When would you use synchronous REST communication versus asynchronous messaging between enterprise applications? Which failure modes influence that decision?
Asked once · last asked Oct 21 · Concept · Senior
How would you design the event-driven data flow so users are notified when a payment status changes, for example from pending to succeeded?
Asked once · last asked Oct 22 · Design · Senior
How would you handle background work and long-running tasks in an Android shopping app if the user might kill the app during checkout?
Asked once · last asked Oct 23 · Scenario · Senior
What responsibilities can a middleware layer serve between mobile apps and core services, and why might a team build one?
Asked once · last asked Oct 23 · Design · Senior
When building a new full stack feature with a React front end and a Node.js or Java back end, how do you version and evolve the API contract so older clients keep working while you deploy back end changes independently?
Asked once · last asked Oct 24 · Design · Senior
Other ways it was asked
- “When building a new full stack feature with a React front end and a Node.js or Java back end, how do you version and evolve the API contract so older front end clients still work while the back end is deployed independently?”
What is publish-subscribe, and when would you use it?
Asked once · last asked Oct 23 · Concept · Mid-level
What is event-driven design, and when would you use it?
Asked once · last asked Oct 24 · Concept · Mid-level
What is the sliding-window rate-limiting pattern?
Asked once · last asked Feb 11 · Concept · Mid-level
In an order-processing flow that uses a queue, what should the first and second messages represent?
Asked once · last asked Mar 19 · Design · Mid-level
How would you determine the maximum queue size for a notification batching system?
Asked once · last asked Mar 31 · Scenario · Mid-level
When would you use cron jobs to schedule tasks?
Asked once · last asked Apr 17 · Concept · Mid-level
What information should a client provide in an object-storage PUT request, such as the bucket name, object key, and payload?
Asked once · last asked Apr 22 · Design · Mid-level
What is an API, why is it important for building scalable web applications, and what is a simple example of how you might use one?
Asked once · last asked May 8 · Concept · Junior
How can local devices communicate with central servers in an application?
Asked once · last asked Jun 11 · Concept · Mid-level
How would you determine the interval for checking whether an asynchronous process has stabilized?
Asked once · last asked Jul 5 · Scenario · Senior
Other ways it was asked
- “How would you monitor whether an asynchronous system has stabilized, and what indicators would you look for?”
In a task graph, how would you define a child task?
Asked once · last asked Jul 22 · Concept · Mid-level
What processing should happen before an application sends a request to Twilio?
Asked once · last asked Jul 26 · Concept · Mid-level
How would webhook callbacks fit into an asynchronous label-generation flow?
Asked once · last asked Aug 11 · Design · Mid-level
What are polling mechanisms?
Asked once · last asked Aug 22 · Concept · Junior
Would you perform transaction matching directly in a worker or enqueue a separate job, and why?
Asked once · last asked Aug 26 · Design · Mid-level
Other ways it was asked
- “Does the worker do the transaction matching right away, or does it kick off a new job to handle that?”
How does the asynchronous job pattern work with multiple vendors?
Asked once · last asked Aug 26 · Design · Senior
What is polling, and when would you use it?
Asked once · last asked Sep 4 · Concept · Junior
How can a system retrieve checksums for file validation from an API or a database?
Asked once · last asked Sep 10 · Concept · Mid-level
In web authentication, what do stateful and stateless mean?
Asked once · last asked Sep 12 · Concept · Junior
Why might a document traceability system use REST APIs?
Asked once · last asked Sep 14 · Concept · Junior
Where should frontend-to-gateway traffic routing be handled?
Asked once · last asked Sep 21 · Design · Mid-level
How can separate services and resolvers be used to handle requests in a GraphQL API?
Asked once · last asked Sep 21 · Concept · Senior
How do push notifications work?
Asked once · last asked Sep 30 · Concept · Mid-level
How do we implement background jobs?
Asked once · last asked Oct 14 · Design · Mid-level
More System Design interview questions
- All System Design interview questions
- System Design Fundamentals Interview Questions
- Software Architecture Interview Questions
- Microservices and Integration Interview Questions
- Database and Data Pipeline System Design Interview Questions
- Scalability and Reliability Interview Questions
- Cloud Architecture and Multitenancy Interview Questions
- AI System Design Interview 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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