133 Reverse Proxy and Load Balancing

A reverse proxy is a reliability boundary: it enforces routing policy, mediates failures, and protects backend services.

Request Path

client -> edge proxy -> route match -> upstream selection -> backend
                     -> policy layer (auth, limits, timeout)

Routing Model

Keep routing deterministic and debuggable:

Exact routes first.
Prefix/wildcard routes second.
Explicit default/fallback behavior.

Upstream Selection

Round-robin is a baseline, but production systems also need health awareness:

Remove failing nodes quickly.
Reintroduce nodes only after recovery checks.
Prevent hot-spotting during partial outages.

Timeout and Retry Boundaries

Proxy retries can multiply load if misconfigured. Always apply:

Attempt limits.
Retryable method/status rules.
Total request budget cap.

Why This Chapter Matters

Most distributed outages are coordination failures across otherwise healthy components. A well-designed proxy reduces blast radius by making policies explicit and centrally observable.