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perf(qa): reuse cached non-target content on QA slug-targeted rebuilds despite feed drift - #2057
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…s despite feed drift
QA rebuilds ran ~10min (vs prod ~90s) for a single-slug preview. Root
cause: the content-cache fast path (decideFastPath) disables on a feed
fingerprint mismatch (catalog/tag-labels), forcing a full regen of all
~2100 tutorials. QA rebuilds are infrequent while prod republishes on
every merge, so by each QA run the catalog has drifted and the
fingerprint almost always mismatches — chronically defeating the fast
path. (The slug-filter Phase-2 scoping already works on QA; the full
regen, not discovery, was the cost.)
Add decideFastPath({ allowFeedDrift }) and set it for channel === 'qa'
only. On QA slug-targeted runs the fast path now reuses cached
non-target pages despite feed drift (the target slug is always
regenerated). Trades slightly-stale nav/tags on OTHER preview pages
(corrected on the next full QA rebuild) for a ~90s targeted preview.
Prod keeps strict feed-freshness (allowFeedDrift defaults false).
Tests: +4 decideFastPath cases (allowFeedDrift eligible on drift; still
requires sidecar + slug-targeted). 18 content-cache tests pass.
This was referenced Aug 27, 2026
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Problem
QA slug-targeted rebuilds take ~10 min vs prod's ~90s for the same single-tutorial change. Investigation of run 33103082513 (per-step timing + full log):
[slug-filter] scoped Phase 2 to 1 repo(s)); discovery is not the cost.[content-cache] fast path disabled — feed fingerprint changed. The fingerprint hashescatalog+tag-labels(fetch-tutorials.ts:864). QA rebuilds run rarely while prod republishes on every merge, so by each QA run the catalog has drifted and the fingerprint almost always mismatches → the content-cache fast path is chronically defeated on QA.Fix
Add
decideFastPath({ allowFeedDrift })and setallowFeedDrift: channel === 'qa'. On QA slug-targeted runs the fast path now reuses cached non-target pages despite feed drift (the target slug is always regenerated — its cache is busted upstream). Prod is unchanged (defaults false → strict feed-freshness).Tradeoff (approved)
Non-target QA preview pages may show slightly stale nav/tags until the next full QA rebuild. Acceptable for an author-preview channel; buys ~90s single-slug previews.
Tests
+4
decideFastPathcases (eligible on drift withallowFeedDrift; still requires a sidecar + slug-targeted run). 18 content-cache tests pass. Change is type-clean (only pre-existing baseline@types/nodenoise in these files).