Design a geo-distributed Email System
Last updated: June 6, 2026
Quick Overview
Design a geo-distributed email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Redfin
System Design
Software Engineer
Redfin
June 6, 2026Software Engineer
Onsite
System Design
Medium
8
13
1,175 solved
Design a geo-distributed email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Redfin asks this during the Onsite 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
- 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
High-level architecture and component design
Failure handling and fault tolerance
Consistency models and replication
Partitioning and sharding strategies
API design and rate limiting
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?
- What would the deployment pipeline look like for this system?
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Requirements
Functional Requirements
- Email Sending: Users can send emails to multiple recipients with support for attachments.
- Email Receiving: Users can receive and view emails in their inbox. 3...
Capacity Estimation
Back-of-Envelope Calculation
- Users: Assume Redfin has 10 million active users.
- Emails per User: On average, each user sends or receives 20 emails per day.
- Total Emails: 10 mil...
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