Design a Load Balancing for Robinhood
Last updated: August 6, 2025
Quick Overview
Design a low-latency load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Robinhood
System Design
Software Engineer
Robinhood
August 6, 2025Software Engineer
Technical Screen
System Design
Medium
11
5
3,802 solved
Design a low-latency load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Robinhood 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
- 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
Security and authentication
Load balancing and horizontal scaling
Database selection and data modeling
High-level architecture and component design
Consistency models and replication
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 migrate from a monolithic to a microservices architecture?
- How do you ensure data consistency across multiple services?
- How would you implement rate limiting to protect the system?
- What happens if one of your database nodes goes down?
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Requirements
- Functional Requirements:
- Load balancer should distribute incoming requests evenly across multiple backend servers.
- Support for sticky sessions to maintain user session state.
- Integra...
Capacity Estimation
- Estimating QPS:
- Assume Robinhood has 10 million active users.
- If each user makes an average of 5 requests per minute:
- Total requests = 10M users * 5 requests/user/min = 50 million ...
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