Last updated: August 2026
REST vs gRPC for Microservices: Which to Use?
Use REST for public-facing APIs, third-party integrations, and any client needing broad compatibility and human-readable JSON payloads. Use gRPC for internal service-to-service calls within your own infrastructure where you need lower latency, strict typing via protocol buffers, and native streaming support. Many microservices architectures use both — REST at the public edge, gRPC for internal service-to-service traffic.
Why does REST remain the default for public APIs?
REST's ubiquity is its main advantage — every programming language, every HTTP client, every developer's browser dev tools work with REST out of the box, and JSON payloads are human-readable, which matters enormously for debugging and for third-party developers integrating against your API without deep familiarity with your systems. Public APIs and partner integrations benefit from this low barrier to entry; requiring external consumers to adopt gRPC's protocol buffer tooling and binary format raises the integration cost for every client you want to support.
Why does gRPC win for internal service-to-service calls?
gRPC uses Protocol Buffers, a binary serialization format significantly more compact than JSON, and runs over HTTP/2, which supports multiplexed streams over a single connection — both reduce latency and overhead compared to REST over HTTP/1.1 for high-volume internal traffic. gRPC's strict typing via .proto schema files also catches contract mismatches at compile time rather than at runtime, which matters more inside a microservices architecture where dozens of internal services communicate constantly, and a silent type mismatch between services is harder to catch than one at a well-tested public API boundary.
What does gRPC cost you in exchange for that performance?
gRPC's binary format isn't human-readable without tooling, making ad hoc debugging with curl or a browser significantly harder than REST's plain JSON. Browser support for gRPC directly is also limited — gRPC-Web requires a proxy layer to work from browser clients, adding infrastructure that a pure REST API doesn't need. And gRPC's tooling and mindshare, while mature, is smaller than REST's, meaning fewer engineers arrive already fluent with it, which has real onboarding cost for a team.
Full comparison
| Dimension | REST | gRPC |
|---|---|---|
| Best for | Public APIs, third-party integration | Internal service-to-service calls |
| Format | JSON, human-readable | Protocol Buffers, binary |
| Performance | Good | Faster — smaller payloads, HTTP/2 multiplexing |
| Browser support | Native | Requires gRPC-Web proxy |
| Type safety | Loose, runtime errors possible | Strict, compile-time via .proto |
What Code Ninety does
Code Ninety defaults to REST for public and partner-facing API surfaces and gRPC for internal service-to-service communication within microservices architectures, matching the protocol to the actual consumer of the interface rather than standardizing on one protocol for every use case. Browse Code Ninety's client project case studies across regulated industries. See the enterprise ERP modernization case study for a completed migration of this type.