45 API Validation, Error Handling, and Testing Interview Questions

All 45 questions

When designing a REST API, how do you structure error responses consistently, and which HTTP status codes do you standardize for validation, authorization, and conflicts?
Asked in 2 of 377 interviews · last asked Sep 10 · Scenario · Mid-level
Other ways it was asked
- “How do you choose HTTP status codes for validation errors, authentication versus authorization failures, and resource conflicts, and what error response schema do you standardize on?”
How do you verify data correctness when designing an API?
Asked in 2 of 377 interviews · last asked Jun 24 · Scenario · Mid-level
Other ways it was asked
- “How do you handle validation when designing an API?”
How should a Telegram bot handle an invalid response from a currency API?
Asked once · last asked Jun 6 · Scenario · Mid-level
Other ways it was asked
- “How would you test that a Telegram bot fails safely when a currency API returns an invalid response?”
What approach or framework feature would you use to centralize error handling across 20–30 API endpoints?
Asked once · last asked Mar 5 · Tooling · Mid-level
If the frontend already validates text input, is backend validation still necessary, and why?
Asked once · last asked Mar 10 · Scenario · Junior
How would you handle an invalid value, such as a negative price submitted by a user or a BFF?
Asked once · last asked Mar 20 · Scenario · Mid-level
How would you validate a product request before querying MongoDB, then handle and monitor a product-not-found result?
Asked once · last asked Mar 20 · Scenario · Mid-level
How do you handle validation between React and Spring Boot when a user sends a request from the frontend to the backend?
Asked once · last asked Mar 25 · Scenario · Mid-level
How would you implement a button on a contact form that validates the entered address with the Google Maps API, displays whether it is valid, returns the result before the user saves, and prevents saving until validation succeeds?
Asked once · last asked Apr 4 · Scenario · Senior
How can you detect an invalid response from a currency API?
Asked once · last asked Jun 6 · Scenario · Mid-level
What are the major advantages of FastAPI in terms of validation?
Asked once · last asked Jun 24 · Concept · Mid-level
How would you design and optimize a React component for data loading, form validation, API errors, and performance?
Asked once · last asked Jun 24 · Scenario · Senior
In Node.js with Express, how do you structure error handling so async route failures return consistent responses and don't crash the process?
Asked once · last asked Jun 29 · Scenario · Senior
Can you give an example of an Open Finance payload-validation business rule and explain how you would document it?
Asked once · last asked Jul 16 · Scenario · Mid-level
Which fields should be treated as identifiers in an Open Finance API request, and in what order should they be validated?
Asked once · last asked Jul 17 · Scenario · Mid-level
Why should a consent ID be validated before other fields in an Open Finance request?
Asked once · last asked Jul 17 · Concept · Mid-level
Can you tell me the difference between schema validation, validation, and regulatory validation?
Asked once · last asked Jul 17 · Concept · Mid-level
Can a request pass schema validation but still fail at a later stage?
Asked once · last asked Jul 17 · Concept · Mid-level
At what level should a validation rule such as 'the customer must be over 18' be enforced?
Asked once · last asked Jul 17 · Concept · Mid-level
Other ways it was asked
- “At what level should a validation rule like customer must be over 18 happen?”
How do you consume third-party REST APIs and handle data sanitization and validation in the integration pipeline?
Asked once · last asked Jul 17 · Scenario · Mid-level
How do you approach writing test cases for a PUT endpoint versus a PATCH endpoint?
Asked once · last asked Jul 21 · Scenario · Mid-level
Other ways it was asked
- “How do you approach writing test cases for a GET endpoint versus a POST endpoint?”
In a Laravel application with 200 or more API endpoints, how would you make a common `product_key` parameter mandatory without adding validation to every endpoint?
Asked once · last asked Jul 31 · Scenario · Mid-level
How would you implement custom error handling in a REST API using ASP.NET Core, what mechanisms does it provide, and how do exception filters differ from middleware-based error handling?
Asked once · last asked Aug 5 · Scenario · Senior
When validation fails, how would you structure the API response, including its status code and error shape, so a React client can map errors to individual fields or display a global error?
Asked once · last asked Sep 3 · Scenario · Mid-level
Other ways it was asked
- “When validation fails, how would you structure the API response, including the status code and error shape? How should the React client map that into field-level errors versus a global error?”
How would you handle invalid requests or missing data in a service?
Asked once · last asked Sep 9 · Scenario · Junior
When you see input validation plus DTO mapping, what specific edge cases would you look for that can still cause incorrect behavior or security gaps despite valid inputs?
Asked once · last asked Sep 16 · Scenario · Senior
How do you handle partial success and error reporting when processing a list of records in Apex, so the caller knows which records succeeded and which failed? What mechanism would you use, and how would you structure the result?
Asked once · last asked Sep 17 · Scenario · Senior
How do you handle invalid user input or unexpected API data, and prevent the application from breaking?
Asked once · last asked Sep 20 · Scenario · Mid-level
How would you design and document a clear rubric for reviewers to consistently grade webhook-handling implementations, including required checks, edge cases, and pass/fail criteria?
Asked once · last asked Sep 28 · Scenario · Senior
If Angular submits syntactically valid data but Spring Boot detects that the record already exists, how would you handle the error from the backend through to the frontend?
Asked once · last asked Sep 29 · Scenario · Mid-level
What HTTP status code would you return for a duplicate record, and how would you handle exceptions centrally in Spring Boot?
Asked once · last asked Sep 29 · Concept · Mid-level
How do you ensure healthcare integrations conform to HL7 and FHIR standards and correctly handle XML and JSON payloads?
Asked once · last asked Sep 29 · Scenario · Senior
Other ways it was asked
- “How do you ensure compliance with healthcare integration standards such as HL7, FHIR, XML, and JSON when designing integrations?”
How do you technically implement validation for message contracts based on HL7 and FHIR specifications?
Asked once · last asked Sep 29 · Scenario · Senior
Tell me about a time you ensured HL7 and FHIR compliance in an integration. How did you implement validation and handle challenges?
Asked once · last asked Sep 29 · Behavioral · Senior
How would you handle an exception without exposing internal error details to the user?
Asked once · last asked Oct 2 · Scenario · Mid-level
What response should an API return if required fields are missing or fail validation?
Asked once · last asked Oct 15 · Scenario · Mid-level
How does FastAPI handle request validation, what happens when validation fails, and how can you customize the error response?
Asked once · last asked Oct 15 · Tooling · Mid-level
What are the data type differences between PostgreSQL and Oracle, including character types and length, and what is the impact on the API side?
Asked once · last asked Oct 16 · Concept · Mid-level
How should an app handle an ingredient that an API returns as null?
Asked once · last asked Oct 19 · Scenario · Mid-level
An endpoint receives a user's ID, debt, and payment amount. What would you validate before processing the request, and how would you protect the payment process?
Asked once · last asked Oct 20 · Scenario · Senior
In a Python FastAPI service, where would you enforce request validation and error mapping?
Asked once · last asked Oct 22 · Concept · Mid-level
In Java, how do you typically structure exception handling in a Spring Boot REST API?
Asked once · last asked Oct 24 · Tooling · Mid-level
Other ways it was asked
- “In Java, how do you typically structure exception handling in a Spring Boot REST API so errors are consistent, secure, and easy for clients to consume?”
How would you validate user input sent from a client to a backend?
Asked once · last asked Aug 21 · Scenario · Junior
How do you handle errors and exceptions in API responses?
Asked once · last asked Aug 22 · Scenario · Mid-level
How would you handle different error codes returned by a network API?
Asked once · last asked Oct 12 · Scenario · Mid-level

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 REST API 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.

377 interviews, 243 candidates, Jan 2026 to Oct 2026. Updated every month with new interviews.

All 45 questions

When designing a REST API, how do you structure error responses consistently, and which HTTP status codes do you standardize for validation, authorization, and conflicts?

How do you verify data correctness when designing an API?

How should a Telegram bot handle an invalid response from a currency API?

What approach or framework feature would you use to centralize error handling across 20–30 API endpoints?

If the frontend already validates text input, is backend validation still necessary, and why?

How would you handle an invalid value, such as a negative price submitted by a user or a BFF?

How would you validate a product request before querying MongoDB, then handle and monitor a product-not-found result?

How do you handle validation between React and Spring Boot when a user sends a request from the frontend to the backend?

How would you implement a button on a contact form that validates the entered address with the Google Maps API, displays whether it is valid, returns the result before the user saves, and prevents saving until validation succeeds?

How can you detect an invalid response from a currency API?

What are the major advantages of FastAPI in terms of validation?

How would you design and optimize a React component for data loading, form validation, API errors, and performance?

In Node.js with Express, how do you structure error handling so async route failures return consistent responses and don't crash the process?

Can you give an example of an Open Finance payload-validation business rule and explain how you would document it?

Which fields should be treated as identifiers in an Open Finance API request, and in what order should they be validated?

Why should a consent ID be validated before other fields in an Open Finance request?

Can you tell me the difference between schema validation, validation, and regulatory validation?

Can a request pass schema validation but still fail at a later stage?

At what level should a validation rule such as 'the customer must be over 18' be enforced?

How do you consume third-party REST APIs and handle data sanitization and validation in the integration pipeline?

How do you approach writing test cases for a PUT endpoint versus a PATCH endpoint?

In a Laravel application with 200 or more API endpoints, how would you make a common `product_key` parameter mandatory without adding validation to every endpoint?

How would you implement custom error handling in a REST API using ASP.NET Core, what mechanisms does it provide, and how do exception filters differ from middleware-based error handling?

When validation fails, how would you structure the API response, including its status code and error shape, so a React client can map errors to individual fields or display a global error?

How would you handle invalid requests or missing data in a service?

When you see input validation plus DTO mapping, what specific edge cases would you look for that can still cause incorrect behavior or security gaps despite valid inputs?

How do you handle partial success and error reporting when processing a list of records in Apex, so the caller knows which records succeeded and which failed? What mechanism would you use, and how would you structure the result?

How do you handle invalid user input or unexpected API data, and prevent the application from breaking?

How would you design and document a clear rubric for reviewers to consistently grade webhook-handling implementations, including required checks, edge cases, and pass/fail criteria?

If Angular submits syntactically valid data but Spring Boot detects that the record already exists, how would you handle the error from the backend through to the frontend?

What HTTP status code would you return for a duplicate record, and how would you handle exceptions centrally in Spring Boot?

How do you ensure healthcare integrations conform to HL7 and FHIR standards and correctly handle XML and JSON payloads?

How do you technically implement validation for message contracts based on HL7 and FHIR specifications?

Tell me about a time you ensured HL7 and FHIR compliance in an integration. How did you implement validation and handle challenges?

How would you handle an exception without exposing internal error details to the user?

What response should an API return if required fields are missing or fail validation?

How does FastAPI handle request validation, what happens when validation fails, and how can you customize the error response?

What are the data type differences between PostgreSQL and Oracle, including character types and length, and what is the impact on the API side?

How should an app handle an ingredient that an API returns as null?

An endpoint receives a user's ID, debt, and payment amount. What would you validate before processing the request, and how would you protect the payment process?

In a Python FastAPI service, where would you enforce request validation and error mapping?

In Java, how do you typically structure exception handling in a Spring Boot REST API?

How would you validate user input sent from a client to a backend?

How do you handle errors and exceptions in API responses?

How would you handle different error codes returned by a network API?

More REST API interview questions

How this list is made

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