Design a Search for Roblox
Last updated: March 31, 2026
Quick Overview
Design a fault-tolerant search system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Roblox
March 31, 20268
8
4,616 solved
Design a fault-tolerant search system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
ML system design at Roblox goes beyond model selection. This System Design Round 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
- 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
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 the cold start problem?
- How would you run A/B tests on different model versions?
- How would you debug a model that works well offline but poorly online?
- What would you do if model performance degrades over time?
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Requirements
Functional Requirements:
- Search Query Handling: The system should support keyword-based searches for games, user profiles, and virtual items on Roblox.
- Personalized Results: Implement ...
Capacity Estimation
Capacity Estimation:
Assuming Roblox has about 200 million monthly active users, with an average of 10 search queries per user per month:
- Total Search Queries per Month: 200M users * 10 quer...
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