Using environment variables to store sensitive information is a well-known bad practice that seems to be ignored by the "the twelve factor app" manifesto. We will dissect on why this is a bad practice, and why it is not a solution for the problems it tries to solve.

Usage of numeric unique identifiers is a very popular approach to identify individual records in database systems. However, these identifiers can lead to collisions between multiple database instances. In this tutorial, we show a simple mechanism to generate unique numeric keys per cluster.

Dependency injection (DI) is a well known and broadly used pattern to provide dependencies to a given object, following inversion of control principles. In this tutorial you will learn how to build a simple but powerful DI system in Python.