@Override
    public V get(K key) {

        V value = cacheAccessor.get(key);

        if (value == null) {
            value = redisCache.get(key);

            if (value != null) {
                cacheAccessor.put(key, value);
            }
        }

        return value;
    }

private final ConcurrentHashMap<K, ReentrantLock> keyLocks = new ConcurrentHashMap<>();

public V get(K key) {
        V value = cacheAccessor.get(key);

        if (value == null) {
            // Acquire a lock for this key
            ReentrantLock lock = keyLocks.computeIfAbsent(key, k -> new ReentrantLock());
            lock.lock();

            try {
                // Double-check to see if the value has been added by another thread
                value = cacheAccessor.get(key);

                // If the value is not in the cache, fetch it from Redis server and set it in client-cache
                if (value == null) {
                    value = redisCache.get(key);

                    if (value != null) {
                        cacheAccessor.put(key, value);
                    }
                }
            } finally {
                lock.unlock();
            }
        }

        return value;
    }