Design Tweet Search
Last updated: August 10, 2025
Quick Overview
Design the architecture for Tweet Search. Cover scalability, data storage, caching, and real-time requirements.
Twitter/X
August 10, 202547
7
3,288 solved
Design the architecture for Tweet Search. Cover scalability, data storage, caching, and real-time requirements.
This ML system design question from Twitter/X'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
- Design the full ML lifecycle from data collection to model monitoring
- Address cold start, exploration/exploitation, and model freshness
- Discuss multi-objective optimization and ranking systems
- Plan for model debugging, fairness, and bias mitigation
- Design the feature store and training pipeline for scale
- Address model versioning, canary deployments, and rollback strategies
- Discuss the data flywheel and long-term system evolution
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 run A/B tests on different model versions?
- How would you ensure fairness and reduce bias in the model?
- What would you do if model performance degrades over time?
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Requirements
- Functional Requirements:
- Users must be able to search for tweets using keywords, hashtags, and user handles.
- The system must support filtering results by date, relevance, and engagement ...
Capacity Estimation
Assuming Twitter/X has approximately 450 million daily active users (DAUs) and an average of 5 searches per user per day, we can estimate:
- Total Searches per Day: 450M users * 5 searches/user =...
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