Judo Payments offers a platform to build complete mobile payment solutions and host applications with a Judo marketplace. The Android SDK assists in embedding Judo Payments functionality into Android applications. The SDK methods are fully documented on Judo's site. The SDK is compatible with Android version 3.0 or later and requires a developer API key for use.
This tutorial from the FINRA Technology website explains how even novice developers can create a basic REST service for evaluating whether a number is a prime or not. The service is built using automated computing service AWS Lambda, as well as AWS API Gateway and IAM for authentication.