Architect a low-latency File Storage Engine
Last updated: July 16, 2025
Quick Overview
Design a low-latency file storage system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Discord
System Design
Software Engineer
Discord
July 16, 2025Software Engineer
Technical Screen
System Design
Easy
127
6
3,321 solved
Design a low-latency 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
- Map the business problem to a concrete ML objective
- Propose reasonable features and a baseline model
- Discuss basic model evaluation metrics
- Outline a simple serving architecture
Key Topics to Cover
ML objective formulation and metric selection
Model serving and latency optimization
Feedback loops and model retraining
Monitoring and model degradation detection
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- 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?
- What would you do if model performance degrades over time?
- How would you debug a model that works well offline but poorly online?
- What is your model retraining strategy?
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Requirements
- Functional Requirements:
- Store and retrieve files with low latency (less than 100ms).
- Support versioning of files to allow rollback.
- Provide APIs for file upload, download, and...
Capacity Estimation
- Estimating Request Load:
- Assume Discord has 500 million active users. If 10% are accessing the file storage system simultaneously, that’s 50 million users.
- If each user performs an a...
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