Lots of good replies already, but I would also consider a senior engineer someone who puts the team first. They admit mistakes early, look for ways to improve n

Lots of good replies already, but I would also consider a senior engineer someone who puts the team first. They admit mistakes early, look for ways to improve not only the codebase but the software development lifecycle and their teammates as well. Mentor younger engineers, write and maintain thorough documentation. Add processes to reduce risk of shipping faulty code, and preventing production incidents.