Design a low-latency Notification System
Last updated: June 14, 2026
Quick Overview
Design a low-latency notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Zoom
System Design
Machine Learning Engineer
Zoom
June 14, 2026Machine Learning Engineer
Onsite
System Design
Medium
2
15
1,157 solved
Design a low-latency notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Zoom asks this during the Onsite to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.
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
Load balancing and horizontal scaling
API design and rate limiting
Partitioning and sharding strategies
Monitoring, logging, and alerting
Database selection and data modeling
High-level architecture and component design
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 happens if one of your database nodes goes down?
- What monitoring and alerting would you set up on day one?
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Requirements
Functional Requirements
- Real-time Notifications: The system must deliver notifications to users in real-time with latencies of less than 100 milliseconds.
- User Preferences: Users sho...
Capacity Estimation
Back-of-Envelope Calculations
- User Base: Suppose Zoom has 200 million users.
- Notifications per User: On average, each user receives 10 notifications per day.
- **Total Notifications...
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