sync.Mutex vs sync.RWMutex: choose based on read/write ratio

Using sync.Mutex for a data structure that is read far more often than written serialises all readers unnecessarily, reducing throughput.

Use sync.RWMutex when reads dominate. Lock() for writes, RLock() for reads:

type SafeCache struct {
    mu    sync.RWMutex
    store map[string]string
}

func (c *SafeCache) Get(key string) (string, bool) {
    c.mu.RLock()
    defer c.mu.RUnlock()
    v, ok := c.store[key]
    return v, ok
}

func (c *SafeCache) Set(key, value string) {
    c.mu.Lock()
    defer c.mu.Unlock()
    c.store[key] = value
}

RWMutex allows multiple concurrent readers. A plain Mutex lets only one goroutine in at a time regardless of whether it reads or writes. For read-heavy workloads, this is a significant throughput bottleneck.