Design an ad exchange that runs a real-time auction across many bidders within a 100ms budget.

When a page loads, an ad slot goes to auction across dozens of bidders and a winner is picked before the page finishes rendering, all in under 100ms. The design covers the auction mechanism, the brutal latency budget, budget pacing, and fraud. Here is how an exchange runs millions of auctions per second.

Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.