Ask Sendai

Since 2009, Square has enabled quick and easy credit card payments to small businesses. Four years ago, the company branched out into peer-to-peer transactions via its Cash App. After some steady growth, the app rocketed in popularity in 2016, reaching millions of users over just a few months and landing at the top of the App Store downloads. The only problem? “We had a large monolith of a few hundred thousand lines of code that was built on the assumption of one single MySQL database; it was never really designed to scale from the start,” says Engineering Manager Jon Tirsen.