API Architecture

Design and govern APIs across the stack: REST/GraphQL/gRPC protocol selection, versioning strategies, rate limiting, security, documentation, and developer experience optimization.

Guiding Principle

"APIs are the product — every endpoint is a contract, every breaking change is a trust violation, every missing doc is a support ticket."

Procedure

Step 1 — API Style Selection & Design

1. Evaluate API style per use case: REST (CRUD resources), GraphQL (flexible queries), gRPC (high-perf inter-service)
2. Define resource naming conventions and URL structure
3. Design request/response schemas with consistent envelope patterns
4. Specify error response format: error codes, messages, field-level details
5. Implement pagination strategy: cursor-based, offset-based, or keyset

Step 2 — Versioning & Evolution

1. Select versioning strategy: URI path, header, query parameter, or content negotiation
2. Define backward compatibility rules: additive-only for minor versions
3. Design deprecation process: timeline, communication, sunset headers
4. Implement API changelog generation from spec diffs
5. Establish breaking change review process with consumer notification

Step 3 — Security & Rate Limiting

1. Design authentication strategy per API tier: API keys, OAuth 2.0, JWT
2. Implement authorization: scopes, RBAC, or ABAC per endpoint
3. Design rate limiting: per-client, per-endpoint, with burst allowance
4. Implement input validation and sanitization at the gateway layer
5. Define CORS, CSP, and security header policies

Step 4 — Developer Experience & Governance

1. Generate OpenAPI/AsyncAPI specifications from code or design-first
2. Build interactive API documentation with try-it-out capabilities
3. Provide SDK generation for primary consumer languages
4. Design API catalog with discovery, search, and dependency tracking
5. Establish API design review process with style guide enforcement

Quality Criteria

• All APIs have OpenAPI/AsyncAPI specifications with >90% endpoint coverage
• Rate limiting tested under load with documented behavior at limits
• Breaking changes go through deprecation cycle with >30-day notice
• API documentation includes runnable examples for every endpoint

Anti-Patterns

• Inconsistent naming conventions across different API surfaces
• Versioning by creating entirely new API copies instead of evolution
• Rate limiting without communicating limits in response headers
• API documentation generated but never tested or maintained