Zomato — Mock Interview

You're designing Zomato for a live system-design interview — a food-delivery marketplace connecting three sides in real time: eaters hunting for something nearby, restaurants cooking, and delivery partners ferrying orders across a live city.

Scale assumptions:

• ~40M DAU; ~10M orders/day; each session runs a handful of discovery searches.
• ~500k restaurants (a small, slowly-changing catalog); ~100 menu items each.
• ~300k riders online at peak, each streaming GPS every ~4 s (~75k location writes/s).
• Targets: discovery < 200 ms p99; a rider assigned within a few seconds; the map fresh within ~5 s.

Two problems make this hard beyond a normal checkout: geospatial discovery (which open restaurants can serve this location, fast) and real-time delivery logistics (pick the best rider from thousands of moving dots and keep the eater's map live). Think out loud, state your assumptions, and call out where you'd separate reads from writes.