The Lock That Left Too Soon Debugging Lab

The Lock That Left Too SoonReliabilityEasyPreparing workspaceAutosaved

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Incident Dossier

The Lock That Left Too Soon

Two transactions serialize on the same key. The first commits, returns success, and yet a second transaction started immediately afterward reads the pre-commit value because the lock was already gone.

Initial failing signallock is dropped before commit appliesExpected holdsLock(a) === true during commit · received holdsLock(a) === false during commit

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Run npm test.
Trace commit: notice the lock entry is deleted before the pending writes are applied.
Hold the lock through the entire commit, including the post-commit observation point.
Release the lock only after the data is visible.

Focus Mode

Start

src/transaction.js

Likely area

src/transaction.js

Progressive hints

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

TopicReliability

DifficultyEasy

Est. time14 min

Workspacecreating

Explorer

Preparing workspace files…

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$ workspace boot

Workspace booting...