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Node.js wasn’t selected because it is easier to scale the team with a JVM base. Node.js isn’t developed enough to have standards and best practices, a large volume of well tested code. With Scala you can use all the Java code. There’s not a lot of knowledge of how to use it in a scalable way and they target 5ms response times, 4 9s HA, 40K requests per second and some at 400K requests per second. There’s a lot in the Java ecosystem they can leverage.