Design a food delivery system

Design a food delivery platform (similar to common restaurant delivery apps).

Core user stories

1. Customers can browse restaurants/menus, place an order, pay, and track delivery.
2. Restaurants receive orders, confirm/prepare them, and update status.
3. Delivery partners (couriers) receive assignments, navigate to pickup/dropoff, and update status.

Functional requirements

• Restaurant discovery (basic search/filter by location/cuisine).
• Menu retrieval.
• Order placement and payment.
• Order lifecycle: CREATED -> CONFIRMED -> PREPARING -> READY_FOR_PICKUP -> PICKED_UP -> DELIVERED (include cancellation/refund paths).
• Real-time-ish tracking/status updates for customers.

Non-functional requirements

• High availability for placing orders.
• Idempotency for order creation/payment.
• Low latency for dispatch.
• Support peak traffic (e.g., lunch/dinner spikes).

Follow-ups (mentioned by interviewer)

1. How would you design the dispatch/matching between orders and couriers?
2. How would you model and deliver real-time order status updates?
3. How would you scale search and read-heavy restaurant/menu traffic?
4. Optimization follow-up: Couriers have limited capacity/time; choose a subset of candidate orders to batch/assign to maximize value under constraints (this can resemble a knapsack -style optimization). Explain your approach at a high level.