Design a real-time Messaging System
Last updated: May 2, 2026
Quick Overview
Design a real-time messaging system handling millions of requests. Discuss consistency, availability, and performance trade-offs.
Walmart
System Design
Software Engineer
Walmart
May 2, 2026Software Engineer
System Design Round
System Design
Easy
707
3
3,100 solved
Design a real-time messaging system handling millions of requests. Discuss consistency, availability, and performance trade-offs.
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.
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Practice System Design ProblemsSample Answer
Requirements
Functional Requirements:
- Real-time messaging: Users should be able to send and receive messages instantly.
- Group messaging: Support for group chats and channels.
- User presence...
Capacity Estimation
Assuming Walmart has around 300 million active users:
- Daily Active Users (DAU): 10% of active users = 30 million.
- Peak Concurrent Users: Assume 10% of DAU = 3 million users online at pea...
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