Design a large-scale Inventory Management Platform

Last updated: August 18, 2025

Quick Overview

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

Roblox
System Design
Software Engineer
Roblox
August 18, 2025
Software Engineer
Onsite
System Design
Medium

10

5

4,976 solved


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

This ML system design question from Roblox's Onsite tests your ability to think about ML systems at scale. The interviewer expects discussion of data quality, feature stores, model serving infrastructure, and A/B testing strategy.

What the Interviewer Expects
  • Define clear ML objectives with appropriate loss functions and metrics
  • Design a comprehensive feature engineering pipeline
  • Discuss model selection with trade-offs (complexity vs interpretability vs latency)
  • Plan online and offline evaluation strategies including A/B testing
  • Address serving infrastructure: batch vs real-time, latency requirements
  • Consider data quality, labeling strategy, and feedback loops
Key Topics to Cover
Model serving and latency optimization
A/B testing and experimentation
Feature engineering and feature stores
Model selection and architecture
Feedback loops and model retraining
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
  • What would you do if model performance degrades over time?
  • How would you handle a 10x increase in prediction requests?
  • How would you run A/B tests on different model versions?
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Sample Answer
Requirements

Functional Requirements

  1. Inventory Tracking: Maintain real-time inventory levels for millions of virtual items across various games.
  2. User Interface: Provide a responsive UI for users ...
Capacity Estimation

Assuming Roblox has approximately 100 million active users:

  • Peak Concurrent Users: 10% concurrent usage leads to 10 million users at peak.
  • Requests per User: Each user could generate about...

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