Design Notification Infrastructure for microservices
Last updated: July 6, 2025
Quick Overview
Design a real-time notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Mastercard
System Design
Software Engineer
Mastercard
July 6, 2025Software Engineer
Onsite
System Design
Medium
100
11
3,807 solved
Design a real-time notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Mastercard 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
Caching strategies (local, distributed, CDN)
Monitoring, logging, and alerting
Load balancing and horizontal scaling
High-level architecture and component design
Message queues and async processing
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 migrate from a monolithic to a microservices architecture?
- How do you ensure data consistency across multiple services?
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Requirements
Functional Requirements:
- Real-time Notifications: The system must deliver notifications to users in real-time across various channels (e.g., SMS, email, mobile push).
- *User Preferences...
Capacity Estimation
Back-of-Envelope Calculations:
- Daily Active Users (DAU): Assume 10 million daily active users.
- Notification Events: If each user generates 5 notifications per day, that’s a total of ...
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