Describe the most critical failed release you have worked on.

The most critical failed release occurred due to insufficient testing of new functionality that affected a key system module. As a result, after deployment, there were operational failures, leading to service downtime and negative impacts on users.

Main reasons:

• Insufficient coverage by automated tests.
• Lack of comprehensive testing in an integration environment.
• Underestimation of the impact of changes on related components.

Lessons learned: strengthened code review processes, expanded the set of automated tests, implemented staged deployment with Canary releases, and monitoring metrics for quick problem detection.