Production Concerns

From “it works” to “it ships”

You can define a service, generate stubs, implement a handler, and call it — and it works on your laptop. Production asks harder questions: How do you log and authenticate every call without editing every handler? How do you encrypt traffic and prove who the caller is? How do you spread load across many backends when gRPC deliberately holds one long-lived connection? This module answers those.

What this module covers

Lesson	What you’ll learn
Interceptors	The middleware model — wrap every call for logging, auth, metrics, retries
Security & Auth	TLS and mTLS for the channel, token auth per call, and why they’re separate
Metadata	Key/value headers and trailers — auth tokens, trace ids, request ids
Load balancing & health	Why L4 balancers break gRPC, client-side LB, and health checking

The theme: cross-cutting concerns

Everything here is a cross-cutting concern — something every RPC needs but no single handler should own.

flowchart LR
  call["incoming call"] --> tls["TLS / auth"]
  tls --> intc["interceptors
(log, metrics)"]
  intc --> md["metadata
(trace id, token)"]
  md --> handler["your handler
(business logic)"]
  handler --> lb["load balancing
spreads calls across backends"]

Cross-cutting concerns wrap the business logic, not live inside it

gRPC gives you first-class hooks for each so your handlers stay focused on business logic. Learn these and your service becomes observable, secure, and scalable without rewriting the code that does the actual work.

🛰️ Why this module matters

The difference between a demo and a service is almost entirely cross-cutting: security, observability, and scale. gRPC bakes hooks for all three into the framework — interceptors, credentials, metadata, and load-balancing policies — so you configure them once instead of scattering them through every method.

What do all the topics in this module have in common?

They change the .proto schema They are cross-cutting concerns — needed by every call, owned by no single handler They only apply to streaming RPCs They are database features

Why should logging and auth live in interceptors rather than each handler?

Handlers cannot access metadata So handlers stay focused on business logic and the concern is applied once Because gRPC forbids logging in handlers To make the .proto smaller

What makes load balancing uniquely tricky in gRPC?

gRPC has no clients gRPC deliberately holds one long-lived multiplexed connection, which a naive L4 balancer pins to one backend gRPC cannot use TLS gRPC only runs on one machine

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