Design an Email Campaign Delivery System
Last updated: October 30, 2025
Quick Overview
Design a system like Mailchimp that enables businesses to create, schedule, and send marketing email campaigns to millions of subscribers with analytics tracking.
Intuit
System Design
Software Engineer
Intuit
October 30, 2025Software Engineer
Onsite - System Design
System Design
Hard
15
11
4,930 solved
Design a system like Mailchimp that enables businesses to create, schedule, and send marketing email campaigns to millions of subscribers with analytics tracking.
Relevant for Mailchimp teams. Focuses on high-throughput message delivery, ISP rate limiting, deliverability optimization, and real-time analytics at scale.
What the Interviewer Expects
- Design for sending billions of emails with high deliverability rates
- Handle ISP-specific rate limiting and reputation management
- Support campaign scheduling, A/B testing, and segmented audiences
- Implement real-time open/click tracking and analytics dashboards
- Address bounce handling, unsubscribe compliance (CAN-SPAM, GDPR), and spam prevention
Key Topics to Cover
Email Deliverability
Rate Limiting
Event Tracking
ISP Reputation
Compliance
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 a situation where a major ISP starts throttling your sending IP?
- How do you prevent a single bad actor from damaging sending reputation for all customers?
- What is your strategy for warming up new IP addresses?
- How would you implement predictive send-time optimization?
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Practice System Design ProblemsSample Answer
Requirements
Functional Requirements
- Campaign Creation and Scheduling: Users can create, edit, and schedule email campaigns.
- Subscriber Management: Users can manage subscriber lists, including se...
Capacity Estimation
Assuming Intuit aims to send 5 billion emails per month:
- Daily Email Volume: 5 billion / 30 days = 166.67 million emails/day.
- Hourly Email Volume: 166.67 million / 24 hours = 6.94 million ...
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