The code itself matters far less than the team and the culture around it. Code will be different in 5 years, a quality culture should not.
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I'm intrigued to see that Google has quantified that new code is generally buggier and less secure than code that has existed in your codebase for longer: https://security.googleblog.com/2024/09/eliminating-memory-safety-vulnerabilities-Android.html
Over a sufficiently long time horizon, all code you write is legacy code.
It's really satisfying to use a profiler for the first time on a project. I always find a big performance win with only a small code change.
It's never the code that I expected to be slow, however!