In April 2025, Nos developed an atomic upsert operation, insert_or_assign_if, for the ConcurrentHashMap class in the facebook/folly repository. This feature enables safe insert-or-update semantics with a predicate check, addressing common concurrency challenges in C++ development. By reducing boilerplate and minimizing race conditions in upsert patterns, Nos improved both correctness and performance for high-concurrency code paths. The implementation leveraged advanced data structures and concurrency techniques, and was delivered as a dedicated commit after thorough review and targeted testing. Nos’s work demonstrated a focused, in-depth approach to enhancing folly’s concurrency primitives, with no major bug fixes required during the period.