During September 2025, Sergey Zelenov focused on enhancing the reliability and data integrity of Change Streams in the mongodb/node-mongodb-native repository. He addressed a critical bug in the ChangeStream.tryNext() method, ensuring correct caching of the resumeToken after each processed change. This work involved refactoring core ChangeStream logic and expanding integration test coverage, including scenarios with simulated network errors. Using JavaScript, TypeScript, and MongoDB, Sergey improved the resilience of real-time data streaming by reducing inconsistencies and strengthening error handling. His contributions enabled more robust data pipelines, minimizing the risk of missed changes in applications relying on Change Streams.