Question 1

What is an API client and why do I need one?

Accepted Answer

An API client lets you send HTTP requests, view responses, and save requests for reuse. Much better than testing in browser devtools or curl. Essential for building and debugging APIs efficiently.

Question 2

Postman, Insomnia, or Hoppscotch?

Accepted Answer

Postman is the most feature-rich but heavy and increasingly subscription-focused. Insomnia is lighter and open source. Hoppscotch is web-based and fully free. Insomnia or Hoppscotch for most startup needs.

Question 3

How do I organize API requests?

Accepted Answer

Create collections by project or API domain. Use folders for related endpoints. Name requests clearly (GET users, POST create order). Use environment variables for base URLs and auth tokens.

Question 4

What are environment variables in API clients?

Accepted Answer

Variables that change between contexts: dev vs staging vs production URLs, different API keys. Switch environments easily without editing requests. Essential for testing across multiple environments.

Question 5

How do I handle authentication in API testing?

Accepted Answer

Store tokens in environment variables. Most clients support OAuth flows, API keys in headers, and bearer tokens. Set auth at collection level to apply to all requests. Never commit real tokens to version control.

Question 6

What is REST vs GraphQL?

Accepted Answer

REST uses multiple endpoints for resources (GET /users, POST /orders). GraphQL uses one endpoint where clients request exactly the data they need. REST is simpler; GraphQL is more flexible. Most startups use REST.

Question 7

How do I test error handling?

Accepted Answer

Send invalid requests intentionally: wrong auth, missing fields, invalid data. Verify your API returns proper error codes (400, 401, 404, 500) and helpful error messages. Test edge cases before users find them.

Question 8

What are pre-request and post-request scripts?

Accepted Answer

Scripts that run before/after requests. Use pre-request to generate dynamic data or set timestamps. Use post-request to save response data to variables for subsequent requests. Powerful for complex workflows.

Question 9

How do I share API collections with my team?

Accepted Answer

Export and version control collections with your code. Postman and Insomnia have team sync features. Keep collections updated as your API evolves. Shared collections become documentation and testing standards.

Question 10

What is API mocking?

Accepted Answer

Creating fake API responses for development before the real API is ready. Useful when frontend and backend are developed in parallel. Postman and Insomnia support mock servers.

Question 11

How do I document my API?

Accepted Answer

Use OpenAPI/Swagger specification for structured documentation. Tools like Readme or Mintlify generate docs from specs. Or export Postman collections as documentation. Good docs reduce integration support burden.

Question 12

What are webhooks and how do I test them?

Accepted Answer

Webhooks are APIs that call your server when events occur (payment received, user signed up). Test with services like webhook.site to inspect incoming requests. Ngrok exposes your local server for webhook testing.

Question 13

How do I test rate limits?

Accepted Answer

Send many requests quickly to trigger limits. Verify you get appropriate 429 responses. Test your client's retry logic. Important for both building rate-limited APIs and consuming third-party APIs.

Question 14

What is Postman performance?

Accepted Answer

Postman can run collections with multiple iterations and concurrent virtual users for load testing. Useful for basic performance testing before dedicated load testing tools. Identifies slow endpoints early.

Question 15

How do I version my API?

Accepted Answer

Include version in URL (/v1/users) or header. Make breaking changes in new versions. Support old versions for transition periods. Document version differences. Plan for versioning from the start.

Question 16

What HTTP status codes should my API return?

Accepted Answer

200 OK for success, 201 for created, 400 for bad request, 401 for unauthorized, 403 for forbidden, 404 for not found, 500 for server error. Use codes correctly—clients rely on them for error handling.

Question 17

How do I handle file uploads in APIs?

Accepted Answer

Use multipart/form-data for file uploads. API clients support file attachments. Consider size limits and validation. For large files, use signed URLs for direct upload to cloud storage.

Question 18

What is an API gateway?

Accepted Answer

A server that sits in front of your APIs handling routing, rate limiting, auth, and monitoring. AWS API Gateway, Kong, and others. Startups often don't need this initially—add when API complexity warrants it.

I need to build and test APIs

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