Design a food delivery platform (DoorDash/Uber Eats).

Restaurant catalog: MongoDB for flexible menu structure (different item types) Real-time location: Redis Geospatial for restaurant and driver locations Orders: PostgreSQL for ACID payment and order state machine Order status: Redis Pub/Sub for real-time status updates to customer Cart: Redis Hash with TTL (30 min) Delivery assignment: Redis sorted set of available drivers by distance ETAs: Redis f