The five-year mile

fiveyearsdev is named for a simple idea: there’s a mile-marker in an engineer’s career — somewhere around year five — where you stop reciting memorized answers and start reasoning from first principles. That’s the bar this site is built around.

Every article takes one thing a strong engineer should know — a system design, a data structure, a piece of the runtime — and explains it properly: why it works, where it breaks, and the trade-offs an interviewer is really probing. No 200-tab study plans.

Two things stay consistent throughout: the reasoning comes first (derivations and invariants, not flashcards), and the code is real — browsable end to end in a read-only viewer, and downloadable in full.