If you're serious about API design, then learn these 20 concepts: 1 Endpoint 2 HTTP Methods 3 Request-Response 4 Status Codes 5 Authentication 6 Authorization 7 Access Tokens 8 OAuth 2,0 9 Rate Limiting 10 Throttling 11 Pagination 12 Caching 13 Idempotency 14 Webhooks 15 API Versioning 16 OpenAPI 17 REST vs GraphQL 18 API Gateway 19 Microservices 20 Error Handling API is a set of rules that allows different services to communicate with each other. What else should make this list?

@systemdesignone Include validation, security, and monitoring. Add scalability patterns and lifecycle management.