Worked on stabilizing the ChangeStream Review feature in the awslabs/amazon-documentdb-tools repository, focusing on backend reliability and error handling using Python. Addressed a scenario where the review loop could crash if no changes were detected, particularly in idle or catch-up states. The solution involved initializing the currentTs variable to None and providing clear user feedback when no qualifying changes were found, preventing calculation errors such as UnboundLocalError or zero-division. Maintained the existing workflow without refactoring, following maintainer guidance for a minimal-guard fix. Demonstrated careful debugging and defensive programming while improving logging and overall system stability for users.