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Design an On-Demand Delivery Platform

MetaSoftware Engineer · Onsite
MediumSoftware EngineerOnsiteSystem Design

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This question evaluates skills in designing scalable, reliable distributed systems with emphasis on state management (shopping cart persistence), real-time telemetry (courier location updates), workflow orchestration (order lifecycle and dispatch), and operational concerns like scalability and reliability.

Design an on-demand local delivery marketplace for restaurants or grocery stores.

The platform should support customers browsing merchants, building shopping carts, placing orders, merchants preparing orders, couriers accepting assignments, real-time courier tracking, and customer notifications.

Focus especially on the following areas:

  1. Shopping cart persistence
  • A customer may add items from web or mobile, close the app, switch devices, or lose network connectivity.
  • The cart should be recoverable later.
  • Discuss consistency, expiration, anonymous carts, logged-in carts, and conflict resolution.
  1. Courier location updates
  • Couriers continuously send GPS updates while online and during deliveries.
  • Customers and internal dispatch systems need near-real-time location.
  • Discuss ingestion, storage, fanout, rate limiting, and privacy.
  1. Order lifecycle and dispatch
  • Orders move through states such as cart, placed, accepted by merchant, ready, courier assigned, picked up, delivered, or canceled.
  • Discuss how services communicate and how you prevent invalid state transitions.
  1. Scalability and reliability
  • The system should handle high traffic during meal-time peaks.
  • Discuss APIs, data models, core services, queues or streams, caching, failure handling, observability, and trade-offs.