I went straight for the data model and probably should have spent more time clarifying scope first.
Start by clarifying the scope and requirements of the cart system, such as whether it's for a single restaurant or multi-restaurant, user authentication, and real-time updates. Then, propose a high-level design covering data models, APIs, and storage, and dive into key components like consistency, scalability, and trade-offs. Finally, discuss how to handle edge cases like item availability changes and concurrent modifications.
Pro tip: Emphasize idempotency and conflict resolution strategies, as carts often involve concurrent updates from multiple devices. Also, consider how to handle price changes and item availability in real-time, which is crucial for food delivery.
Ask questions to understand functional and non-functional requirements, such as expected scale, consistency needs, and integration with other services like menus and payments.
Outline the main components: client, API gateway, cart service, database, and cache. Sketch how data flows between them.
Define the cart data model, including items, quantities, modifiers, and pricing. Decide on storage (e.g., SQL vs NoSQL) based on access patterns and consistency requirements.
Discuss scalability, consistency (e.g., using optimistic locking or versioning), and real-time updates (e.g., WebSockets or polling). Address how to handle item availability and price changes.
Summarize trade-offs made (e.g., consistency vs availability) and cover edge cases like concurrent edits, cart expiration, and multi-device sync.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.