track /04-sql-lost-updates

Two Writers, One Row

Concurrency does not announce itself in tests that run one request at a time. Oversell the inventory on purpose, then make it impossible.

Intermediate ~7h postgresqlpythondocker

Your evidence lives here

Sign in, enroll, and rehearse the failures on purpose — kill the worker, publish the duplicate, pull the queue out from under it. What you paste here is what says you did.