Design Notification Infrastructure for global users
Last updated: July 28, 2025
Quick Overview
Design a high-throughput notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Pinterest
System Design
Product Manager
Product Manager
Technical Screen
System Design
Medium
7
11
2,192 solved
Design a high-throughput notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Pinterest 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
Message queues and async processing
Failure handling and fault tolerance
High-level architecture and component design
Caching strategies (local, distributed, CDN)
Database selection and data modeling
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 would you handle a 10x increase in traffic overnight?
- How would you handle a region-wide outage?
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Requirements
- Functional Requirements:
- Users should receive notifications for various activities such as likes, comments, follows, and repins.
- Notifications must be delivered in real-time or near real...
Capacity Estimation
- Estimating Peak Load:
- Assuming Pinterest has around 500 million users, with an average of 20 notifications per user per day, we get:
- Total notifications per day = 500 million * 20 = 10...
- Assuming Pinterest has around 500 million users, with an average of 20 notifications per user per day, we get:
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