Architect a event-driven Email Engine
Last updated: June 4, 2026
Quick Overview
Design a event-driven email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
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Design a event-driven email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
LinkedIn asks this during the System Design Round 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
- 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 monitoring and alerting would you set up on day one?
- How would you handle a 10x increase in traffic overnight?
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Requirements
Functional Requirements
- Event Processing: The system must process email events triggered by user actions (e.g., new connections, messages, job alerts).
- Email Composition: Provide tem...
Capacity Estimation
Assuming LinkedIn has approximately 900 million users and estimating that daily active users (DAU) is around 10%:
- DAU = 90 million users.
- If 10% of DAU generates email events, we can expect about ...
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