Loading…
Design an Ad Serving System is a hard system design interview question covering Distributed Systems, ranking, real-time, caching, Databases — the kind asked at FAANG (Facebook/Meta, Apple, Amazon, Netflix, Google) and AI-first companies like Anthropic, OpenAI, and Nvidia.
Design a system that selects and serves an ad for each incoming request. About 100,000 requests per second at peak, a few million active creatives from around 100,000 advertisers, and a hard 50ms internal latency budget inside the publisher's 100ms exchange deadline. Ads are targeted by boolean predicates, ranked by bid multiplied by predicted click-through rate, and sold by second-price auction. Advertiser budgets must pace across the day and may only be overspent by a small bounded amount, and clicks reported by an untrusted client must never be over-billed.
Interactive walkthrough on Pro
Upgrade to Pro to unlock the clarifying questions, architecture, capacity calculations, tradeoffs, follow-up answers, and the model answer.
What's inside this guide
Design rounds are decided on capacity estimates. Both tools are free.
Fully unlocked, no account needed — solutions, walkthroughs and follow-up answers included.
Or start the Study Plan — a week-by-week order for your loop, and week 1 is entirely free.
A full interview loop is more than one round. These are the others, each with what is on the site for it.