Andres is a great coworker to have at Citus Data, though I first ran into him on the mailing lists shortly after starting at Citus myself. I was tasked with figuring out "why do certain read-only workloads fail miserably under high concurrency?"

I had never touched PostgreSQL before, nor any Linux performance tools, but I noticed that replacing certain buffer eviction locks with atomic implementations could drastically help this particular case. I emailed the list about it and Andres was someone who chimed in with helpful advice. I wrote up what I'd discovered in my deep dive here: http://tiny.cc/postgres-concurrency

Turns out Andres was already working on a "better atomics" patch to provide easier methods of using atomic operations within PostgreSQL's code base (my patch was a quick hack probably only valid on x86, if that). It's been useful in removing several performance bottlenecks and—two years in—it looks like it's still paying off.