Design a food ordering and delivery system

Design a backend system for a **food ordering + delivery** platform (like a marketplace that connects customers, restaurants, and delivery couriers). ## Core user flows 1. Customer: - Browse/search restaurants and menus - Add items to cart, place an order, pay - Track order status (prep, picked up, arriving) 2. Restaurant: - Receive order, accept/reject, update prep status 3. Courier: - Receive delivery offers, accept, pickup, deliver ## Requirements ### Functional - Restaurant/menu discovery (basic search/filter is enough) - Order creation and payment intent - Reliable order state machine (created → accepted → preparing → ready → picked_up → delivered/cancelled) - Dispatch: assign courier to an order - Real-time-ish tracking and status updates to customer ### Non-functional - High availability (avoid single points of failure) - Consistent order state (no double-deliver, no lost orders) - Handle peak traffic (lunch/dinner bursts) - Observability: metrics, logs, tracing ## Deliverables - APIs (high level) - Data model (high level) - Architecture and major components - Approach to scaling, reliability, and failure handling (explicitly call out single points of failure) - Consistency model choices and trade-offs