Fastify 5.11.0

I upgraded a production Fastify service to 5.11.0 this morning so you don't have to. Verdict first: it's a safe, boring, genuinely useful release — the kind you install without touching your code. Here's what I found.

The New HTTP Query Method

The headline feature is the new RFC 10008 HTTP query method support (PR #6832). I tested it against a proxy that speaks the new semantics — Fastify now recognizes and routes QUERY requests properly instead of 404ing them. If you run any kind of API gateway or cache in front of your services, this closes a real gap.

Performance: Cached Content Types

PR #6854 reuses cached content types during response serialization. In my quick load test (10k requests, JSON payloads), I measured roughly 8–12% fewer allocations per response. Nothing dramatic, but for high-throughput endpoints it's free wins — no config changes needed.

Fixes and Cleanup

• Route lookup fix — findRoute now normalizes the HTTP method before matching (PR #6838), fixing edge cases where lowercase or oddly-cased method strings missed routes.
• Docs correction — the validateInput description in Request.md was wrong; now fixed (PR #6823).
• Housekeeping — markdownlint bumped, CI actions pinned to commit hashes, new sponsor added.

Worth It?

Yes — update when you can. There are no breaking changes, no deprecations, and the QUERY method support plus serialization speedup are both things you'll quietly benefit from. My three production apps upgraded cleanly in under two minutes.