If they have two million servers that would mean about 1000 daily active users per server. Assuming the average user makes 2000 requests (API calls, images, vid

If they have two million servers that would mean about 1000 daily active users per server. Assuming the average user makes 2000 requests (API calls, images, videos, etc.) a day mindlessly browsing the infinite feed, that works out to about 1 request per second. Facebook makes its money from advertisers so that's likely where most of the compute resources are going - users just see the ads at the end of all that computation. Combined with the mandatory over provisioning, the overhead of a massive distributed systems, tracing, etc, I'm not surprised those are the numbers. Assuming each server cost an average of $20k, that's $40 billion which is two quarters worth of revenue but amortized over 5+ years. It's really not all that much.