Amazon OOD Interview: Restaurant System with Custom Orders

Design a scalable, object-oriented restaurant management system that covers the customer journey from reservations through payment. You are asked to model domain entities (tables, reservations, menu items, orders, payments, staff) and their interactions so the system remains flexible when handling high-volume, concurrent activity such as peak dinner hours.

Core expectations

• Model table management with assignment, reservation lifecycle (create/modify/cancel), and status tracking (free, reserved, occupied) while preventing double-booking.
• Model a menu and customizable items (e.g., pizzas) where customizations follow validation rules (each topping type may be added only once per pizza), sizes, crusts, availability, and dynamic pricing.
• Support order creation and processing (dine-in linked to table, pickup, delivery with address/driver), order state transitions, modifications before preparation, and reliable payment processing with discounts and taxes.

Interview flow / staging

You will typically: (1) clarify requirements and constraints, (2) sketch domain model (classes, relationships), (3) propose APIs/services for reservations, orders, menu, and payments, (4) discuss concurrency, validation and persistence strategies, and (5) explain scaling and fault-tolerance choices.

Skill signals to demonstrate

You should show strong domain modeling, OOP design (composition over inheritance), validation logic (prevent duplicate toppings), use of repository or DAO patterns for persistence, concurrency control (transactions/optimistic locking) and performance/scalability techniques (caching, partitioning, async processing). Use clear, modular abstractions so adding menu items or order types is low-cost.