Incident Dossier

Cache invalidated before the write commits

After updating a user's name, the cache keeps returning the old value. The cache update happens before the write commits (with the pre-write snapshot), so the next read returns stale data.

Initial failing signalAfter updateUserName the cache still returns the old nameExpected behavior: getUser(1).name === 'alice2' after updateUserName(1, 'alice2') · actual behavior: getUser(1).name === 'alice' (the pre-write snapshot)

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Run npm test.
Notice that after updateUserName the next getUser still returns the old name.
Inspect updateUserName in src/users.js.
Find where the cache is primed and what snapshot it uses.
Prime the cache with the freshly-committed row instead of the pre-write snapshot.

Focus Mode

Start

src/users.js

Likely area

src/users.js

Challenge Coach

Hints reveal broad direction first, then narrow toward the suspect path without showing hidden tests or exact solution code.

TopicCaching & Performance

DifficultyEasy

Est. time15 min

Workspacepreparing

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Evidence Map

Failing signal loaded from challenge API
Workspace files loaded from workspace API
Results rendered only after API run/submit

Autosaved

workspace

Outputread-onlyready$ prepare workspace

Preparing workspace