Design Inventory Management Infrastructure for mobile apps

Last updated: August 24, 2025

Quick Overview

Design a event-driven inventory management system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Pinterest
System Design
Software Engineer
Pinterest
August 24, 2025
Software Engineer
System Design Round
System Design
Hard

252

10

4,883 solved


Design a event-driven inventory management system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

This is a common system design question asked during System Design Round at Pinterest. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Pinterest values engineers who can think about scalability from day one.

What the Interviewer Expects
  • Drive the design discussion proactively with minimal interviewer guidance
  • Perform detailed capacity estimation and use it to inform design decisions
  • Design for global scale with multi-region deployment and data consistency
  • Deep dive into 2-3 critical components with implementation-level detail
  • Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
  • Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
  • Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Security and authentication
API design and rate limiting
High-level architecture and component design
Database selection and data modeling
Load balancing and horizontal scaling
Caching strategies (local, distributed, CDN)
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • How do you ensure data consistency across multiple services?
  • What happens if one of your database nodes goes down?
  • How would you migrate from a monolithic to a microservices architecture?
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Sample Answer
Requirements
  • Functional Requirements:
    • Event Handling: The system must handle inventory updates in real time, including additions, removals, and modifications of inventory items.
    • **API for Mobile ...
Capacity Estimation
  • User Base: Assuming 50 million active users with an average of 2 inventory interactions per user per day, we estimate:
    • Total Requests per Day: 50M users * 2 interactions = 100M requests ...

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