Start by clarifying functional and non-functional requirements, then sketch a high-level architecture with core services (restaurant search, order, dispatch, payment, tracking). Dive deep into the most challenging components like geospatial matching for courier dispatch and real-time tracking, discussing trade-offs and scalability.
Pro tip: Emphasize the importance of location-based indexing (e.g., geohashing) and event-driven architecture for real-time updates, as these are critical for DoorDash's core operations.
Ask questions to understand scope: user base, order volume, latency requirements, consistency needs, and key features like search filters, payment methods, and tracking granularity.
Outline main components: API gateway, microservices for restaurant search, order management, dispatch, payment, and tracking, along with databases, caches, and message queues.
Explain how to match couriers to orders using geospatial indexing (e.g., geohash, Quadtree), real-time location updates, and algorithms for optimal assignment considering distance, courier availability, and order priority.
Describe how to provide real-time order status updates using WebSockets or server-sent events, with a pub/sub system to broadcast location and status changes to users.
Discuss trade-offs between consistency and availability (e.g., CAP theorem), database choices (SQL vs NoSQL), and scaling strategies like sharding, caching, and load balancing.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.