Design a large-scale Notification Platform
Last updated: February 19, 2026
Quick Overview
Design a high-throughput notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Apple
System Design
Software Engineer
Apple
February 19, 2026Software Engineer
Technical Screen
System Design
Medium
447
12
1,800 solved
Design a high-throughput notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Apple asks this during the Technical Screen 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
Message queues and async processing
Partitioning and sharding strategies
High-level architecture and component design
Consistency models and replication
Monitoring, logging, and alerting
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 schema migrations with zero downtime?
- What happens if one of your database nodes goes down?
- How would you implement rate limiting to protect the system?
- How would you handle a region-wide outage?
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Requirements
- Functional Requirements:
- The system must support sending notifications (push, SMS, email) to millions of devices simultaneously.
- Users should be able to manage notification preferences (...
Capacity Estimation
- Back-of-envelope calculations:
- Assuming each user receives 5 notifications per day on average.
- For 100 million active users, total notifications = 100 million * 5 = 500 million notificat...
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