PgLoom Tool Detects PostgreSQL Double-Spend Race Conditions in About 60ms

A developer has published a write-up on PgLoom, a tool that finds double-spend race conditions in PostgreSQL-backed wallet withdrawal endpoints without requiring changes to application code. The tool explores transaction interleavings over the wire protocol, reproduces a concrete failure where two withdrawals overdraw a balance, and prints a step-by-step execution trace. It also suggests fixes such as a pessimistic row lock or a guarded atomic UPDATE, and saves a replayable schedule for teams and CI pipelines. The article argues that SERIALIZABLE isolation can cause retry storms on hot rows and side-effect hazards in legacy code, so targeted locking is often preferred under high load. PgLoom can also deliberately trigger serialization conflicts to verify that retry logic works.