The Flash Attention Free-Lunch

Senior AI Engineer interview at NVIDIA, and the interviewer asks:

“Your team wants to ship a new inference speedup for your long-context agent. Every speedup has a hidden cost. What are the three costs you check for, and why does Flash Attention pass the first two when most methods don’t?”

Don’t say: “I’d benchmark latency and memory. Flash Attention is just a faster, optimized kernel.”