Who are the API consumers?
│
├── Public API / Multiple platforms
│   └── REST + OpenAPI (widest compatibility)
│
├── Complex data needs / Multiple frontends
│   └── GraphQL (flexible queries)
│
├── TypeScript frontend + backend (monorepo)
│   └── tRPC (end-to-end type safety)
│
├── Real-time / Event-driven
│   └── WebSocket + AsyncAPI
│
└── Internal microservices
    └── gRPC (performance) or REST (simplicity)

Comparison

Factor	REST	GraphQL	tRPC
Best for	Public APIs	Complex apps	TS monorepos
Learning curve	Low	Medium	Low (if TS)
Over/under fetching	Common	Solved	Solved
Type safety	Manual (OpenAPI)	Schema-based	Automatic
Caching	HTTP native	Complex	Client-based