Always document mutex fields and their purpose, ensure proper locking/unlocking patterns, and avoid redundant locks when underlying structures are already thread-safe. When using mutexes, clearly indicate what data they protect and why the synchronization is necessary. Add comments for mutex fields explaining their purpose: ```go // sendfilesMutex protects concurrent access to sendfiles slice sendfilesMutex sync.RWMutex ``` Avoid redundant locking when underlying structures already provide thread safety: ```go // The mu mutex in the Middleware struct might be redundant for operations // on the Session since Session struct itself already ensures thread-safety ``` Use proper defer patterns to prevent race conditions, even if slightly slower: ```go mutex.Lock() defer mutex.Unlock() // Prevents race conditions on shared data access return c.Status(fiber.StatusOK).JSON(data) ``` Consider performance implications when choosing between `sync.Map` and regular maps with `RWMutex`, but prioritize correctness and clarity over micro-optimizations.