Go: What is the difference between mutex and RWMutex?

Mutex — exclusive lock. RWMutex — concurrent reads, exclusive writes.

sync.Mutex:

• Lock()/Unlock() — one at a time.
• Lower overhead.

sync.RWMutex:

• RLock()/RUnlock() — concurrent reads.
• Lock()/Unlock() — exclusive writes.
• Higher overhead.

1// Mutex
2var mu sync.Mutex
3mu.Lock()
4defer mu.Unlock()
5
6// RWMutex
7var rwmu sync.RWMutex
8rwmu.RLock()
9defer rwmu.RUnlock()

When to use RWMutex:

• Read-heavy workloads.
• Caches.

When to use Mutex:

• Write-heavy workloads.
• Simple cases.

Common mistakes:

• Using RWMutex for write-heavy work.
• Copying mutex.
• Forgetting defer Unlock().
• Not benchmarking.
• Using RWMutex for single-goroutine.