For the backend of the app, Flask is chosen as it is written in Python and easily integratable with machine learning applications, as many ML frameworks are written in python. As well, Flask is quick and easy to setup, with many options for scaling it out to production. For the data, PostgreSQL will be used as it is integratabtle with Heroku since Heroku offers it as an add-on. It is also flexible and supports different data types such as JSON.