mlrequest (https://mlrequest.com) was created to provide an easy (but powerful) machine learning API for any production app, regardless of language or platform. No servers or dependencies required.
I was able to accomplish this in about a month because I had already created part of it for another project. I used AWS to rapidly prototype using their services (cognito, ec2, elasticache, etc.) . Very excited to get some initial feedback and hopefully power many apps with machine learning.