Design Email Infrastructure for mobile apps
Last updated: July 3, 2025
Quick Overview
Design a low-latency email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Confluent
July 3, 202549
3
3,237 solved
Design a low-latency email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during Technical Screen at Confluent. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Confluent values engineers who can think about scalability from day one.
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 implement rate limiting to protect the system?
- What would the deployment pipeline look like for this system?
- What monitoring and alerting would you set up on day one?
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Requirements
Functional Requirements
- Email Sending: Users must be able to send emails through the mobile app.
- Email Tracking: Users should receive notifications for email delivery status (sent, d...
Capacity Estimation
Assuming Confluent has 10 million active mobile users, we estimate the following:
- Daily Email Requests: If each user sends an average of 5 emails per day, total requests = 10M users * 5 emails ...
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