Protocol Comparison: gRPC vs REST vs GraphQL vs Message Queues

Dimension	gRPC	REST	GraphQL	Message Queues
Protocol	HTTP/2, binary protobuf	HTTP/1.1 or HTTP/2, text JSON	HTTP/1.1 or HTTP/2, text JSON	AMQP, MQTT, proprietary
Coupling	Tight (shared proto contracts)	Loose (HTTP conventions)	Medium (shared schema)	Loose (message schemas)
Browser Support	Limited (gRPC-Web proxy)	Native	Native	Not applicable
Streaming	Full (all four patterns)	Limited (SSE, WebSockets)	Subscriptions (WebSockets)	Pub/Sub, streaming
Tooling	Code generation, reflection	OpenAPI, Postman, curl	GraphiQL, Apollo Studio	Broker-specific consoles
Discoverability	Server reflection, proto files	Self-describing with HATEOAS	Introspection queries	Schema registries
Contract Enforcement	Compile-time, strict	Runtime, often informal	Runtime, schema-validated	Runtime, schema-optional
Performance	High (binary, multiplexed)	Moderate (text, connection-per-request)	Moderate (text, query complexity)	High (async, batched)
Best For	Internal services, streaming	Public APIs, web clients	Flexible queries, BFF	Async workflows, decoupling