Three things the load path lacked. The retrieval slots had an unbounded
line behind them, so a burst meant silent waiting; past a bounded line, or
after eight seconds in it, a caller now gets 'the library is busy' and a
503 with a retry hint. The paid routes had no per-account ceiling; they
now get one, counted in Redis so every replica sees the same count and
nothing is refused when Redis is absent. And the same library search
asked twice within a minute (a retry, a refresh) went to the library
twice; it is now answered from Redis, with 0 turning that off.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dv6sqaY6Vq3ChZHMem3cnU
