Design a low-latency Messaging System
Last updated: September 30, 2025
Quick Overview
Design a low-latency messaging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Cockroach Labs
September 30, 202541
14
4,799 solved
Design a low-latency messaging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during System Design Round at Cockroach Labs. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Cockroach Labs values engineers who can think about scalability from day one.
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
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 traffic overnight?
- What would the deployment pipeline look like for this system?
- How would you migrate from a monolithic to a microservices architecture?
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Requirements
Functional Requirements
- Messaging API: Provide endpoints for sending, receiving, and deleting messages.
- User Management: Authentication and user profiles to manage user identities. 3...
Capacity Estimation
- User Base: Assume 10 million active users.
- Message Throughput: Estimate 10 messages per user per day, totaling 100 million messages daily or roughly 1,157 requests per second.
- **Stora...
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