Design a Load Balancing Service
Last updated: March 6, 2026
Quick Overview
Design a real-time load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
CrowdStrike
March 6, 2026510
7
3,830 solved
Design a real-time load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at CrowdStrike 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
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
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 region-wide outage?
- What monitoring and alerting would you set up on day one?
- How would you handle a 10x increase in traffic overnight?
- What would the deployment pipeline look like for this system?
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Requirements
Functional Requirements
- Request Handling: The load balancer must distribute incoming traffic across multiple backend servers to optimize resource utilization and minimize response time.
- ...
Capacity Estimation
Assuming CrowdStrike sees an average of 10 million requests per day with peaks reaching up to 50 million requests during critical events:
- Requests per Second: 50 million requests/day translate...
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