Have you ever felt overwhelmed by a large and complex software codebase?

Joining an existing team with a large, unfamiliar codebase can be daunting, especially when there’s little documentation and poor test coverage.

I was recently tasked with adding a new feature to a project and it took me an unusually long time to complete. I wasn’t struggling because of my knowledge of the framework used or programming language, but because I didn’t fully understand how the project was designed or its various user workflows. It was my first time seeing this codebase and the tight delivery deadline only added to the pressure.

To get past this, I began searching how to quickly understand large, complex codebases. Here are a few key insights I’ve gathered. I call this 𝗧𝗼𝗽 𝗗𝗼𝘄𝗻 𝗔𝗽𝗽𝗿𝗼𝗮𝗰𝗵

𝟭. 𝗨𝗻𝗱𝗲𝗿𝘀𝘁𝗮𝗻𝗱 𝘁𝗵𝗲 𝗣𝗿𝗼𝗷𝗲𝗰𝘁’𝘀 𝗣𝘂𝗿𝗽𝗼𝘀𝗲:
This may sound obvious, but sometime even experienced developers lack a basic understanding of what the system's main purpose is. Focus on understanding the business concepts before diving into the technology. Ask questions like: Who is using the software? What are their main objectives? 𝘊𝘰𝘥𝘦 𝘪𝘴 𝘮𝘦𝘳𝘦𝘭𝘺 𝘢 𝘮𝘦𝘢𝘯𝘴 𝘵𝘰 𝘢𝘯 𝘦𝘯𝘥 𝘢𝘯𝘥 𝘸𝘪𝘵𝘩𝘰𝘶𝘵 𝘬𝘯𝘰𝘸𝘪𝘯𝘨 𝘵𝘩𝘦 𝘦𝘯𝘥 𝘢𝘭𝘭 𝘤𝘰𝘥𝘦 𝘪𝘴 𝘦𝘴𝘴𝘦𝘯𝘵𝘪𝘢𝘭𝘭𝘺 𝘮𝘦𝘢𝘯𝘪𝘯𝘨𝘭𝘦𝘴𝘴.

𝟮. 𝗙𝗮𝗺𝗶𝗹𝗶𝗮𝗿𝗶𝘇𝗲 𝗬𝗼𝘂𝗿𝘀𝗲𝗹𝗳 𝘄𝗶𝘁𝗵 𝘁𝗵𝗲 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲:
Start with the high-level architecture before getting into the details of the each implementation. Understand the different layers, such as the web tier, business tier, and database tier, as well as front-end and back-end. You don’t need to know every technical detail, just enough to get a general understanding of the system’s structure. This can help to create a map of how different piece of technology work together.

𝟯. 𝗗𝗶𝘃𝗲 𝗶𝗻𝘁𝗼 𝘁𝗵𝗲 𝗖𝗼𝗱𝗲:
Begin with the specific code or component you’re working on. Understand what’s its purpose? What functionality does it provide? If available, unit tests can be helpful in understanding how a component works. In well-structured projects, good naming conventions for variables and methods often provide hints about many code flows.

It’s important to remember that this process isn’t immediate - understanding a codebase is iterative. The more you dig into these concepts and understand user journey flows, the easier it gets.

Don’t hesitate to ask for help if you are stuck. Happy coding!😊