## System Design / Data Modeling: Ads Data Model Design the **data model** (logical schema) for an ads platform that supports: - Advertisers creating **campaigns** with **line items** and **creatives** - Targeting (geo, device, content/genre, audience segments) - Budgeting and pacing - Serving and logging events: **impression**, **click**, and optionally **conversion** - Reporting and analytics: spend, delivery, frequency, reach, and performance breakdowns ### What to produce - Key entities and relationships (ER-style description). - Which parts belong to: - an OLTP store (serving/control plane) - an event log / OLAP store (analytics) - Primary keys, important indexes, and partitioning/sharding considerations. - How you would model: - creative rotation and experiments - deduplication/idempotency for events - slowly changing dimensions (e.g., targeting changes) Assume large scale (global traffic) and that reporting must be available with low delay (minutes).