Design a large-scale Chat Platform
Last updated: February 14, 2026
Quick Overview
Design a geo-distributed chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Oracle
System Design
Software Engineer
Oracle
February 14, 2026Software Engineer
Technical Screen
System Design
Easy
7
13
4,440 solved
Design a geo-distributed chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Oracle asks this during the Technical Screen to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.
What the Interviewer Expects
- Clearly define functional and non-functional requirements
- Propose a reasonable high-level architecture with core components
- Choose appropriate data storage solutions with basic justification
- Discuss basic scaling strategies (horizontal scaling, caching)
- Identify potential bottlenecks and suggest simple solutions
Key Topics to Cover
Message queues and async processing
Caching strategies (local, distributed, CDN)
Load balancing and horizontal scaling
High-level architecture and component design
Consistency models and replication
API design and rate limiting
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 do you ensure data consistency across multiple services?
- How would you migrate from a monolithic to a microservices architecture?
- What would the deployment pipeline look like for this system?
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Requirements
- Functional Requirements:
- User authentication and authorization.
- Real-time message exchange (1:1 and group chats).
- Message history retrieval for users.
- Presence indicators (online...
Capacity Estimation
Assuming:
- 1 million active users at peak.
- Each user sends an average of 10 messages/hour.
- Total messages per second = 1,000,000 users * (10 messages/hour / 3600 seconds) = ~2,778 messages/second...
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