gRPC interceptors are the middleware pattern, specialized for gRPC. If you've written HTTP middleware before, the shape is familiar — a function that wraps a call, can observe or modify the request, pass to the next handler, then observe or modify the response. The difference: gRPC's type system makes the flavors (unary, server-stream, client-stream, bidi) explicit, and chain ordering matters more than most people realize. Most online examples show a single toy interceptor. Production systems stack five to ten of them per service. Getting the composition right — ordering, concern separation, testability — is half of running a gRPC-based microservice well. tl;dr — gRPC interceptors are middleware with more explicit types. Chain them outside-in: observability wraps everything, then throttling, then auth, then retry, then the actual service. Keep each interceptor focused on one concern; the moment an interceptor does two things you're writing coupled middleware.…