What is the difference between REST, GraphQL and gRPC?
Quick answer
REST exposes resources over HTTP URLs and is simple and cache-friendly, GraphQL lets clients ask for exactly the fields they need from a single endpoint, and gRPC uses binary Protocol Buffers over HTTP/2 for fast service-to-service calls.
REST is the default for public APIs: it uses standard HTTP methods and status codes, works with browser and CDN caching and is easy to debug. Its weaknesses are over-fetching and under-fetching, which can force clients to make several round trips.
GraphQL solves that for complex front ends, such as mobile apps needing different shapes of data, but caching is harder and you must guard against expensive queries with depth and cost limits. gRPC gives strongly typed contracts, streaming and low latency, which suits internal microservices, but browsers need a proxy to call it directly.