Every codebase eventually faces a brutal test: a new engineer joins, the original author has left, and a critical bug needs fixing under deadline. What you find at that moment reveals whether the original work was professional or merely productive.
Documentation isn't the README
Most projects have a README that tells you how to npm install. Almost none tell you why the architecture is the way it is. The why is what survives turnover.
Useful documentation answers questions like:
- Which problems did we explicitly decide not to solve, and why?
- Where are the brittle integrations and what should you do before touching them?
- What's the actual production environment — not the dev setup?
Tests are a love letter to the next maintainer
A test suite isn't about catching bugs. It's a structured demonstration of how the system is supposed to behave. The maintainer six months from now will read your tests before they read your code.
Architecture you can explain in five minutes
If the next engineer needs three weeks to grok the architecture before they can ship a bug fix, the architecture is wrong. Boring, predictable, layered systems win every time over clever ones.
