How I Approach an Unfamiliar Codebase

The starting point

Opening a large repository and reading files from top to bottom is rarely an efficient way to understand it. I prefer to reconstruct the system's boundaries first. What enters the application? Where are routes defined? Where does data come from? Where are mutations performed? Which parts run on the server and which run in the browser? Once those boundaries are visible, individual files become much easier to place in context.

Start with the runtime path

Find the application entry points and follow one real user action through the system. A public page is a good starting point because it usually reveals routing, data access, rendering, and shared layout. An admin mutation can then show authentication, authorization, validation, and persistence.

The point is to build one complete vertical slice rather than reading every module in isolation. A working mental model of one request is more useful than fifty disconnected facts about utility functions.

Look for ownership boundaries

As you trace the request, ask which module owns each responsibility. If a component directly knows about SQL, if a mutation bypasses authorization, or if configuration is scattered across unrelated files, those are architectural signals. They are not necessarily bugs, but they tell you where assumptions live.

Documentation becomes much more useful after you have this map. You can read a query file and immediately understand which boundary it belongs to instead of treating every file as an isolated puzzle.