Design a multi-tenant Chat System
Last updated: May 9, 2026
Quick Overview
Design a multi-tenant chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Atlassian
May 9, 202660
4
2,151 solved
Design a multi-tenant chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Atlassian asks this during the System Design Round to assess your understanding of the full ML lifecycle. They want to see how you translate a business problem into an ML objective, design the feature pipeline, and plan for model monitoring and retraining.
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 debug a model that works well offline but poorly online?
- What is your model retraining strategy?
- How would you handle a 10x increase in prediction requests?
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Requirements
Functional Requirements
- Multi-tenancy Support: The chat system must support multiple organizations (tenants) with separate chat instances.
- Real-time Messaging: Support instant messag...
Capacity Estimation
Assuming that Atlassian aims to support 10 million active users with an average of 100 messages per user per day:
- Total Messages per Day: 10M users * 100 messages = 1 billion messages/day
- **Me...
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