Worked on the facebook/fbthrift repository to restore Thrift serialization compatibility by reverting experimental optimizations that altered serialization semantics. Addressed a critical bug by rolling back faster serialization methods, ensuring that existing client and server interactions remained stable and service contracts were preserved. Applied backend development expertise and a disciplined rollback strategy, leveraging strong version-control practices to minimize risk of data mismatches across deployments. Demonstrated a deep understanding of serialization and Thrift, using Hack as the primary language. Documented the rollback process thoroughly and prepared the codebase for future evaluation of performance versus compatibility trade-offs, contributing to maintainable and reliable services.