HOW FACEBOOK SERVED BILLIONS OF REQUESTS PER SECOND USING MEMCACHED

Summary from the TLDR Web Dev newsletter

Facebook used Memcached, a key-value store, to efficiently handle billions of requests per second. It achieved this by scaling Memcached at three levels: cluster, region, and worldwide. It used parallel requests and batching, optimized client-server communication, and managed congestion effectively to reduce latency. “Memcache pools” were used to reduce load on their databases.