Page 3 - REST-API

An OpenAPI specification that no longer matches the implementation is worse than no documentation at all, it lies to you. Contract testing closes that gap automatically: tests check on every commit whether the backend implementation still honors the contract the specification defines.

JWT or sessions for Symfony REST APIs? The answer depends on scaling requirements, revocation needs, client type, and security model. Anyone who understands the difference between stateless and stateful authentication can make the right decision for their specific use case.

Poor API error responses cost development time, on both sides. When consumers only get {"error": "Something went wrong"}, they can neither react programmatically nor debug in a targeted way. RFC 9457 Problem Details for HTTP APIs, machine-readable error codes, structured field errors and correlation IDs turn error cases into a first-class feature of the API, not an afterthought.

Documentation that diverges from the code is worse than no documentation at all. Anyone who doesn't maintain OpenAPI schemas, validation rules, and example values in a structured way in Symfony builds up technical debt that discharges with every breaking change. This article shows how to keep schemas, examples, and validation permanently in sync.

A REST API that runs in production but cannot be observed is a black box. Structured logging, distributed tracing with OpenTelemetry and Prometheus metrics are the three pillars that let teams localize errors, explain latency spikes and plan capacity, without digging through log files.

Not every asynchronous requirement needs webhooks. Polling is sometimes the more sensible choice. And REST callbacks exist as a hybrid approach that many teams don't know about. Whoever understands the difference makes better architecture decisions, and doesn't build webhook infrastructure where a simple 30-second poll would be the cleaner solution.

A REST API without correctly documented security requirements is a black box for consumers. OpenAPI 3.x offers four security scheme types that can be made directly usable in the Swagger UI, if you know how to model them correctly, combine them globally and endpoint-specifically, and control them granularly with scopes.

A backoffice API and a public API share HTTP as transport, but their requirements for stability, backward compatibility, security, and error models differ so fundamentally that a unified design inevitably makes one of the two worse.

An OpenAPI specification that exists only for documentation does not get you very far. Anyone who treats it as a binding contract between frontend, backend and external consumers, and hardens it with contract tests, RFC 7807 error formats, security schemas and automated tooling, turns a YAML file into a genuinely productive quality tool.

A technically correct OpenAPI specification is not yet good documentation. Tags structure navigation, examples enable direct integration, schemas validate and explain at the same time, and standardized responses make errors manageable. This guide shows how to get all four dimensions right together.