How do I onboard and get very familiar with the codebase quickly?

Question

I will be starting out as an SDE 1 at Amazon next week and this is my first major job out of college. I have been working mostly on startups and I feel like expectations are high at a big tech company like Amazon. From what I know and from discussions with my HM prior to joining, I will be working with an unfamiliar stack and a lot of internal tools. How do I make the most out of my first week of onboarding, how do I learn the codebase that uses an unfamiliar stack so that I understand it very well and quickly become a valuable contributor to the team? Right now, I'm suffering from imposter syndrome and feel like I might not be good for the job.

Rahul Pandey · Accepted Answer

How to learn a new codebase fast:

Start running the code ASAP. Add a log statement to observe when it gets hit and the state of the variables at that point. DON'T get stuck reading documentation about the language or codebase.
Intentionally break things and understand how they break. Instead of incrementing something by one, increment it by two. Can you explain the result of that change? Understanding the current code is a prerequisite for making your code change.
Land a low-effort code change quickly. Fix a spelling error, modify a comment, or add a unit test. It'll be easier to do your "real" work once you're familiar with the workflow of landing code (and you'll get a confidence boost!)

from my twitter thread

How do I onboard and get very familiar with the codebase quickly?

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