What is gRPC?

Most discussion of APIs concerns the traffic you can see — a browser or a mobile app talking to a server. gRPC lives in the traffic you cannot: services inside a system calling each other, often thousands of times to serve one customer request, where the overhead of each call is multiplied by an uncomfortable number. It addresses that with three choices. Messages travel in a compact binary format rather than as text, which shrinks them substantially. Connections are reused and multiplexed over modern transport, removing per-call setup. And every service publishes its interface in a formal definition file from which client and server code is generated automatically, in whichever language each team uses. That last point is the one with commercial consequences. The interface between two services becomes a checked contract rather than a document somebody hopes is current, so a breaking change is caught at build time instead of at midnight in production. The trade-off is that gRPC is unfriendly to browsers, awkward to inspect by hand, and unnecessary for a system of modest size — which is why it is the right answer for internal high-volume traffic and the wrong answer for a public partner API.