Architect a low-latency File Storage Engine

Last updated: August 4, 2025

Quick Overview

Design a low-latency file storage system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Roblox
System Design
Software Engineer
Roblox
August 4, 2025
Software Engineer
Onsite
System Design
Medium

13

8

341 solved


Design a low-latency file storage system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

ML system design at Roblox goes beyond model selection. This Onsite question evaluates your ability to design end-to-end ML pipelines, from data collection to model serving, while considering production constraints like latency and reliability.

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 selection and architecture
Data collection and labeling strategy
Monitoring and model degradation detection
Feature engineering and feature stores
Online vs offline evaluation
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 would you handle the cold start problem?
  • How would you ensure fairness and reduce bias in the model?
  • How would you run A/B tests on different model versions?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For low-latency File Storage Engine, key functional requirements include:...

Capacity Estimation

Estimate the scale to drive design decisions. Assume 100M DAU with an average of 10 actions per user per day = 1B requests/day ~ 12K QPS average, ~36K...


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