Improve shopping cart latency and stock notifications
Company: J.P. Morgan
Role: Software Engineer
Category: System Design
Difficulty: easy
Interview Round: Take-home Project
You are given an existing e-commerce shopping cart system (web/mobile) that already supports adding/removing items and viewing the cart. The interview focuses on improving the current system rather than rewriting it; you do NOT need to spend much time on full requirements, detailed API specs, or exhaustive data models.
Design improvements to address two problems:
1) **Faster latency** for common cart operations (especially “view cart”).
2) When a product becomes **out of stock**, the system should **notify the user quickly/near real-time** that the item is no longer available (and reflect that state in the cart UI).
Explain your architecture changes, data flow, and how you handle correctness (e.g., avoiding oversells) under high traffic.
Quick Answer: This question evaluates a candidate's ability to design scalable, low-latency e-commerce architectures and real-time notification mechanisms while reasoning about data consistency, concurrency control, and correctness under high traffic (including concerns like avoiding oversells).