What Is gRPC?

gRPC is an open-source remote procedure call (RPC) framework originally developed by Google and released in 2015 as the successor to their internal Stubby system. Instead of asking a service to send you a document like REST does, gRPC lets a client call a method on a remote server as if it were a local function, with the framework handling serialization, transport, and network communication over HTTP/2. It uses Protocol Buffers as its default interface definition language and wire format, which makes payloads compact and calls fast across any language that has a gRPC implementation, including Go, Java, Python, C++, and Node.js.

Every gRPC service starts life as a .proto file, where you define messages (the data structures) and services (the collection of callable methods) using Protocol Buffer syntax. The protoc compiler, or a language-specific plugin, then generates client stub code and server skeleton code from that single definition, so a Python client and a Go server can talk to each other without either team hand-writing serialization logic. This code generation step is what gives gRPC strong typing and cross-language consistency: the .proto file is the single source of truth, and any change to it propagates to every generated client and server after regeneration.

gRPC supports four RPC patterns: unary (one request, one response), server streaming (one request, a stream of responses), client streaming (a stream of requests, one response), and bidirectional streaming (both sides stream independently over the same connection). All four run over a single long-lived HTTP/2 connection, which multiplexes many concurrent calls without the head-of-line blocking that plagued HTTP/1.1, and lets a server push a continuous feed of results, such as live stock prices or sensor telemetry, without the client re-requesting each update.