ASP.NET Core Web API Interview Question #87

What is backward compatibility in API design?

Routing, Versioning, OpenAPI/Swagger & API Documentation Mid-Level Intermediate

Quick Interview Answer

Backward compatibility means existing clients can continue operating correctly after the API is updated. Preserving field meanings, accepted inputs, status-code behavior, and documented endpoint semantics helps avoid breaking consumers.

Detailed Explanation

Backward compatibility means existing clients can continue operating correctly after the API is updated. Preserving field meanings, accepted inputs, status-code behavior, and documented endpoint semantics helps avoid breaking consumers.

Public APIs should be changed cautiously because clients may be deployed independently and cannot necessarily upgrade at the same time as the server.

Code Example

// Prefer additive evolution when safe:
{
  "id": 10,
  "name": "Phone",
  "category": "Electronics"
}

// Existing fields retain their established meaning.