First is an early 30s guy who currently works on search and NLP (amongst other things) and has a PhD in mathematics. He optimizes things for fun, and does it with the same flair and ease a musical virtuoso would do variations on chopsticks.

Second is a mostly retired RPG / CL programmer in his 60s who occasionally contracts to IBM i shops and can make that platform sing like a supercomputer on steroids.

Both are inspiring in different ways.