Design a Load Balancing for Discord
Last updated: January 12, 2026
Quick Overview
Design a distributed load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Discord
System Design
Product Manager
Discord
January 12, 2026Product Manager
Onsite
System Design
Easy
29
11
2,708 solved
Design a distributed load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Discord typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
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
Failure handling and fault tolerance
High-level architecture and component design
API design and rate limiting
Partitioning and sharding strategies
Monitoring, logging, and alerting
Load balancing and horizontal scaling
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 handle a 10x increase in traffic overnight?
- What happens if one of your database nodes goes down?
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Requirements
- Functional Requirements:
- Route incoming requests from users to appropriate backend services (e.g., chat messages, calls).
- Support multiple protocols, including WebSocket and HTTP. 3....
Capacity Estimation
- User Base: Assume Discord has 150 million monthly active users, with 10 million concurrent users during peak times.
- Request Rate: If each active user sends 1 message every 5 minutes, the s...
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