Most web-based services begin as a collection of front-end application servers paired with databases used to manage data storage. As they grow, the databases are augmented with caches to store frequently-read pieces of data and improve site performance. Often, the ability to quickly access data moves from being an optimization to a requirement for a site. This evolution of cache from neat optimization to necessity is a common path that has been followed by many large web scale companies, including Facebook, Twitter1, Instagram, Reddit, and many others.