Everything your team needs, and one teammate that uses all of it

Reads a diff like a staff engineer and says the hard thing

Designs the system you need now and names the trade-off out loud

Hunts the root cause instead of guessing at the symptom

Measures before it optimises, then makes the slow thing fast

Writes the tests that would have caught it, not the ones that pad coverage

Keeps the build green, the deploy boring, and the rollback one command