Design Messaging Infrastructure for global users
Last updated: August 13, 2025
Quick Overview
Design a high-throughput messaging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Compass
System Design
Software Engineer
Compass
August 13, 2025Software Engineer
Onsite
System Design
Medium
7
3
2,473 solved
Design a high-throughput messaging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Compass asks this during the Onsite 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
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
Monitoring, logging, and alerting
API design and rate limiting
High-level architecture and component design
Partitioning and sharding strategies
Message queues and async processing
Requirements gathering and capacity estimation
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
- What would the deployment pipeline look like for this system?
- How would you handle schema migrations with zero downtime?
- How would you migrate from a monolithic to a microservices architecture?
- How do you ensure data consistency across multiple services?
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Requirements
Functional Requirements
- User Messaging: Users can send and receive messages in real-time.
- Group Messaging: Support for group chats with multiple users.
- Message History: Users ...
Capacity Estimation
Back-of-Envelope Calculations
- User Base: Assume 10 million active users.
- Messages per User: Average of 10 messages per user per hour.
- Total Messages: 10 million users * 10 mes...
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