verify_password (Argon2id, OWASP defaults m=19456 KiB, t=2) is CPU-bound
at tens-to-hundreds of ms and was invoked synchronously on the Tokio
worker. Worse, verify_api_key Argon2-verifies every candidate sharing
the 8-char prefix — a hot user with N keys serialized every admin
request behind N×Argon2.
Wrap each call site in tokio::task::spawn_blocking:
- auth_middleware::verify_api_key (per request carrying a Bearer key)
- auth_api::login (admin login)
- users_service::login (data-plane app-user login, both real-hash and
TIMING_FLAT_DUMMY_HASH branches)
Cold-cache login is now ~2× current latency due to one spawn_blocking
hop, but the worker no longer parks on Argon2 so steady-state under
load is dramatically better. The LRU cache for the hot-path (token →
principal) is finding F-P-009 — separate commit.
AUDIT.md anchor: F-P-002.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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