Design a File Storage for Discord

Last updated: May 26, 2026

Quick Overview

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

Discord
System Design
Software Engineer
Discord
May 26, 2026
Software Engineer
Technical Screen
System Design
Medium

159

6

838 solved


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

This ML system design question from Discord's Technical Screen 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
Feedback loops and model retraining
A/B testing and experimentation
Online vs offline evaluation
Feature engineering and feature stores
Training pipeline and infrastructure
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 a 10x increase in prediction requests?
  • How would you run A/B tests on different model versions?
  • What would you do if model performance degrades over time?
  • What is your model retraining strategy?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For File Storage for Discord, key functional requirements include: what a...

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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