I started with the cart and item models which felt safe, but then the pricing piece got messy fast.
Start by clarifying requirements and scope, then model the core domain objects (Cart, CartItem, Customization) and define a PricingEngine that applies a pipeline of composable pricing strategies. Emphasize extensibility, immutability, and a receipt that captures each pricing layer's effect for transparency and debugging.
Pro tip: Discuss how you'd handle pricing strategy ordering and conflicts (e.g., coupon vs. membership discount) and propose a deterministic resolution mechanism, such as priority or explicit sequencing, to avoid ambiguity in production.
Ask questions to understand constraints: expected scale, types of customizations, pricing rules, and whether pricing is computed client-side or server-side. Confirm the need for auditability and real-time updates.
Identify key entities: Cart, CartItem, CustomizationGroup, CustomizationOption, and PriceBreakdown. Specify relationships and invariants, such as a cart containing multiple items, each with selected customizations.
Define a PricingStrategy interface with a method to apply pricing to a cart and return a modified breakdown. Implement concrete strategies for base price, surge, membership discount, and coupons. Use a pipeline or chain of responsibility to compose them.
Create a PriceBreakdown class that records each applied strategy, the amount changed, and the running total. Ensure it supports serialization for display and logging.
Discuss how to add new strategies without modifying existing code (Open/Closed Principle). Consider performance implications of strategy ordering, caching, and concurrency. Mention alternative designs like rule engines or DSLs.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.