Liveness — process is up and the event loop can respond.

2026-06-04: stripped DB-touch and the (non-threadsafe) _health_cache after the sustained-load incident. /health used to call psycopg2.connect(timeout=2) on cache-miss, which under TTL expiration produced a cache stampede across uvicorn workers and blocked the event loop. Now it's async + trivial — cannot block.

For DB-aware readiness, use a separate /readyz endpoint (not deployed yet). Cloudflare + cloudflared + canary all probe /health as a liveness signal, which only needs to confirm the process is serving HTTP.