An expert who knows how to support web and mobile app with minimum duplicate work. o Back end stack: python, flask, selenium, postgres, HTML, Jinja template, etc. o Note these are NOT required for the front end developer. We just need the front end to communicate with back end servers via REST API calls. o But for testing purpose, the developer may need to work on python and selenium code to start a back end server, populate testing date, and confirm testing results.