Design a Notification for Cruise
Last updated: October 28, 2025
Quick Overview
Design a low-latency notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Cruise
October 28, 202519
13
89 solved
Design a low-latency notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Cruise 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
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 optimize costs as the system scales?
- How would you handle a region-wide outage?
- How would you handle a 10x increase in traffic overnight?
- What monitoring and alerting would you set up on day one?
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Requirements
Functional Requirements:
- Real-time Notifications: The system should deliver notifications in real-time to users about ride updates, promotions, and safety alerts.
- User Segmentation: ...
Capacity Estimation
To estimate capacity, we can analyze the expected scale:
- User Base: Assume 1 million active users.
- Notification Frequency: Each user receives an average of 10 notifications per day.
C...
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