499 post-mortem: an O(n) library audit inside a polled GET on a one-core
cgroup, three reverse-proxy hops, and the status no monitor watches.
- measured: 13.6 s idle / 17.7-98.5-35.8 s probes / 76-2507 s under load
- evidence triad: 7x 499 @ portal, zero app-log entries, in-container repro
- fix: 300 s TTL cache + single-flight refresh + refreshing/cached_at flags,
text-first client reader, ?refresh=1
- result: cached path 200 in 0.24-0.36 s (median 0.26 s)
- art: ideogram4 base frame + 4 derived targets, art-meta evidence line
- LinkedIn companion: docs/linkedin/batch-07-linkedin-posts.md
