This is an example of a simple pair of microservices which you can deploy to GOV.UK PaaS.
The backend picks a random image from a subset of the Government Art Collection and the frontend renders a page with the image. Both the frontend and the backend are ruby applications using Sinatra.
The frontend app reads the URL of the backend app from an environment variable called BACKEND_URL.
This is a simple example for us to use in user research into running microservices on the PaaS.