Engineered concurrency control for payment microservice using row-level locks, improving system reliability for 200k+ users. Reduced median, API latency by 250ms.
The Challenge
We had a critical customer-reported bug where payments were failing at a specific time daily. Initial investigation showed no code errors, but the failures were real, indicating a deep system-level conflict.
The Solution
I conducted a deep system analysis and discovered a race condition: a background installment update job was locking database rows at the exact same moment users were trying to pay. I implemented a robust Postgres Row-Level Lock strategy to act as a "traffic cop", ensuring user transactions always took precedence.
⚡ The Impact
This fix completely eliminated the "ghost" payment failures and stabilized the core financial transaction flow for over 200,000 users. It transformed a flaky experience into reliable infrastructure.
System Log End