Real-Time Ad Bidding Systems (RTB): Designing for <100ms Responses

The Millisecond Economy

Every time you load a webpage, an invisible auction happens at speeds that make stock exchanges look slow. Multiple advertisers compete to show you their ad in under 100 milliseconds—faster than you can blink. Miss that deadline by even 50ms, and your bid is worthless. The ad slot goes to someone else, and you’ve wasted compute cycles on a bid that arrived too late.

This isn’t theoretical latency—it’s the real-time bidding (RTB) ecosystem where billions of auctions happen daily, each demanding sub-100ms end-to-end response times. Google’s AdX, Amazon’s AAP, and The Trade Desk process over 10 million bid requests per second at peak, with latency budgets measured in single-digit milliseconds for each hop.