API-First Products implementation checklist

Verify that the OpenAPI 3.0/3.1 specification matches the actual implementation using a tool like Prism or Dredd to prevent drift.

Ensure all error responses follow the RFC 7807 (Problem Details for HTTP APIs) format, including specific error codes and human-readable messages.

Implement 'Idempotency-Key' header support for all POST and PATCH requests to prevent duplicate processing during network retries.

Replace offset/limit pagination with cursor-based pagination for all collection endpoints to ensure consistent performance and data integrity.

Audit all endpoints to ensure consistent casing (e.g., camelCase or snake_case) and pluralization across the entire resource tree.

Verify that API keys are stored using a cryptographically secure hash (like SHA-256) and are never logged or stored in plain text.

Configure global and per-user rate limits at the gateway level (e.g., using Zuplo or Cloudflare) to prevent DoS and manage resource allocation.

Restrict Cross-Origin Resource Sharing (CORS) to specific allowed domains rather than using wildcards in production.

If using JWTs, ensure the backend validates signatures, expiration times, and 'aud'/'iss' claims on every request.

Disable support for TLS 1.0 and 1.1; enforce TLS 1.2 or 1.3 for all incoming API traffic.

Test the integration between the API gateway and the billing engine (e.g., Stripe Billing) to ensure usage events are reported within a <5 minute lag.

Verify that the system returns a 429 Too Many Requests status code immediately when a user exceeds their plan's monthly or daily quota.

Implement signature verification for incoming webhooks from payment providers to prevent spoofing of subscription updates.

Programmatically handle 'past_due' subscription statuses to allow a 3-day grace period before revoking API access.

Ensure every API request is tagged with an internal 'organization_id' derived from the API key to facilitate accurate cost-per-customer analysis.

Implement JSON-based structured logging for all requests, including request IDs, response times, and status codes.

Integrate OpenTelemetry to trace requests across microservices, specifically monitoring latency in AI inference or database calls.

Deploy a /health or /ready endpoint that checks downstream dependencies (DB, Redis, LLM providers) and returns a 503 if any are unreachable.

Set explicit timeouts for all external service calls (e.g., 30s for AI wrappers) to prevent hanging worker processes.

Implement circuit breakers on non-critical downstream services to allow the API to fail gracefully during partial outages.

Set up a CI/CD pipeline to generate and publish TypeScript and Python client libraries whenever the OpenAPI spec is updated.

Deploy a hosted documentation portal (e.g., Mintlify or Stoplight) that allows developers to execute test requests directly from the browser.

Provide a separate 'test' API key mode that interacts with a non-production database for developer integration testing.

Enforce versioning via a custom header (e.g., 'X-API-Version') or URL path to ensure backward compatibility for existing users.

Launch a status page (e.g., Better Stack or Statuspage.io) that reflects real-time uptime and latency of the API endpoints.