Design a search-to-ads ranking pipeline

Prompt

Design a high-level search + ads ranking system for an app where a user issues a query and the product shows a mix of organic search results and sponsored ads.

Requirements

• Return results within a strict latency budget (assume ~200 ms end-to-end).
• Ensure good user experience while meeting monetization goals.
• Support experimentation (A/B tests) and continuous model iteration.

Discuss

1. The main components of the request flow (retrieval, filtering, ranking, mixing).
2. How ads ranking differs from organic ranking (auction/bids, pacing/budgets, policies).
3. How you would mix ads and organic results and what constraints you would enforce.
4. Key metrics to monitor and how you would debug regressions.