In our profession, it’s common to work on an unfamiliar codebase. It happens every time one joins a new project or even needs to work on a previously untouched part in big ones. This occurrence is not limited to a developer having to fix a bug; it can be a solution architect having to design a new feature or an OpenSource contributor working on a GitHub issue in their free time. Hence, I want to describe how I approach the situation so it can benefit others.

It sometimes happen that after a few years, an app is stable enough that it gets into hibernating mode. Though it’s used and useful, there are no changes to it and it happily runs its life. Then, after a while, someone decides to add some new features again. Apart from simple things such as locating the sources, one of the most important thing is to be able to build the app. Though it may seem trivial, there are some things to think about.