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API Best Practices

First PublishedByAtif Alam

Use this page for operational and quality guardrails around APIs. Keep REST HTTP Fundamentals as the contract-surface source of truth (URLs, methods, status, error shape, validation, idempotency).

Security Basics

Section titled “Security Basics”
  • Authenticate clearly at boundaries (user tokens for user-facing APIs, service identity for service-to-service calls).
  • Authorize per resource and action in domain logic, not only at route decorators.
  • Treat secrets as toxic data: never place tokens, API keys, or credentials in URLs or logs.
  • Use TLS everywhere and keep CORS explicit (allowed origins, methods, headers).
  • Rate-limit by principal (token, client, or IP) and return 429 with Retry-After where applicable.

For policy depth, see Security.

Observability Defaults

Section titled “Observability Defaults”
  • Emit structured logs with route, status, latency, and correlation or trace ID.
  • Track RED metrics per endpoint family: request rate, error rate, and duration.
  • Propagate trace context across downstream hops to preserve end-to-end visibility.
  • Distinguish liveness and readiness checks (/healthz vs /readyz style behavior).

For platform-level guidance, see Observability and Observability for systems.

Reliability Behavior

Section titled “Reliability Behavior”
  • Set timeouts by default on inbound handlers and outbound client calls.
  • Retry only when safe: idempotent operations, or write operations with stable idempotency outcomes.
  • Apply exponential backoff with jitter to reduce synchronized retry storms.
  • Respect Retry-After on 429 and overload responses.
  • Pair write endpoints with idempotency key policy and bounded server-side key retention.

For deeper retry and degradation strategy, see Fault tolerance.

Performance Hygiene

Section titled “Performance Hygiene”
  • Prefer cursor pagination on large or changing collections.
  • Support field projection when payloads become wide (for example ?fields=id,name).
  • Use cache headers and ETag where clients and intermediaries can safely reuse responses.
  • Keep connection pools tuned for databases and outbound HTTP clients.
  • Avoid over-nesting resources in URLs and over-joining data in one endpoint by default.

Testing and Rollout Checks

Section titled “Testing and Rollout Checks”
  • Run contract tests against OpenAPI and critical endpoint fixtures.
  • Cover one happy path plus representative edge failures per endpoint (validation, authz, conflict).
  • Keep status and error envelope mapping consistent across handlers.
  • Require explicit deprecation and versioning notes for breaking changes.
  • Add rollout checks for backward compatibility and basic operational dashboards before wider release.

Quick Review Checklist

Section titled “Quick Review Checklist”
  • Security boundaries and secret handling are explicit.
  • Logs, metrics, and trace propagation are present.
  • Timeout and retry policy is documented and safe.
  • Pagination and response size controls are in place.
  • Contract and edge-case tests cover key failure modes.

Where To Go Next

Section titled “Where To Go Next”