Too Long; Didn't Read
Velo is a full-stack development platform that empowers you to rapidly build, manage and deploy professional web apps. To work with external database collections you need to create an external database adapter. This adapter implements a Service Provider Interface (SPI) that enables your site to communicate with your external database collection. The critical steps in the process are steps 2 and 5. You need to build the adapter that implements the SPI and translates requests and responses between the two systems. The adapter takes the request from your site and converts it into something your Wix site can receive.