Build a low-latency Email Pipeline
Last updated: May 20, 2026
Quick Overview
Design a low-latency email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Snapchat
May 20, 202667
15
802 solved
Design a low-latency email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Snapchat 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
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?
- How would you handle a 10x increase in traffic overnight?
- How would you optimize costs as the system scales?
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Requirements
Functional Requirements
- Email Sending: Users should be able to send emails with attachments, rich text, and multimedia content.
- Real-time Notifications: Users should receive notifica...
Capacity Estimation
To estimate capacity for the email pipeline, we consider:
- Daily Active Users (DAU): Assume Snapchat has 300 million DAUs.
- Emails Sent per User: Assume an average of 3 emails sent per user ...
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