5 REST API Mistakes That Cost Me Users

Three years ago, I built my first public API. I thought it was finished in one weekend. I waited for users to arrive.

They came. Then they left.

The product was fine. The API was hard to use. I made five major mistakes. Here is how I fixed them.

  1. Using 200 OK for Errors I sent a 200 OK status even when things failed. I put the error message inside the JSON body. This forced developers to write custom logic for every single call.

The fix: Use correct HTTP status codes.

  • Use 400 for bad input.
  • Use 401 for auth failures.
  • Use 404 for missing resources.
  • Use 429 for rate limits.
  1. Forgetting Versioning I changed my data fields without warning. One change broke every integration I had.

The fix: Prefix your routes with /v1/. This prevents breaking existing clients when you update your code. Keep your current version and one previous version.

  1. No Rate Limiting One buggy script hit my search endpoint 200 times per second. It maxed out my database. It crashed the system for everyone else.

The fix: Implement rate limiting. Use a token-bucket approach. Return a 429 Too Many Requests status with a Retry-After header.

  1. Inconsistent Error Formats My error messages looked different depending on where the error happened. One error used "msg" while another used "message." Developers had to write multiple parsers for one API.

The fix: Pick one error structure and use it everywhere. Every error should have the same keys.

  1. Returning Too Much Data My /users endpoint returned every user in the database. When we hit 10,000 users, the response size crashed mobile apps.

The fix: Use cursor-based pagination. This keeps responses small and stable. It is faster for large datasets than offset-based pagination.

The results:

  • Integration time dropped from 3 days to 4 hours.
  • Support tickets dropped by 70%.
  • Former users came back.

Your API is your product. A good frontend cannot save a bad API.

What is the worst API mistake you have seen? Tell me in the comments.

Source: https://dev.to/sirmax/5-rest-api-mistakes-that-cost-me-users-and-how-to-fix-them-57gi