Design Email Infrastructure for real-time analytics

Last updated: October 7, 2025

Quick Overview

Design a scalable email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Zoom
System Design
Machine Learning Engineer
Zoom
October 7, 2025
Machine Learning Engineer
Technical Screen
System Design
Medium

10

7

2,765 solved


Design a scalable email system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

System design interviews at Zoom 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
Message queues and async processing
High-level architecture and component design
Requirements gathering and capacity estimation
Database selection and data modeling
Load balancing and horizontal scaling
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • How would you handle a region-wide outage?
  • How would you handle a 10x increase in traffic overnight?
  • How would you implement rate limiting to protect the system?
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Sample Answer
Requirements
  • Functional Requirements:
    1. Handle incoming emails for real-time analytics, processing millions of requests per day.
    2. Provide event-driven notifications to trigger analytics workflows (e.g...
Capacity Estimation
  • Estimated Traffic:
    • Assume Zoom processes 10 million emails per day, with an average of 5 seconds per email for processing.
    • This translates to about 115 email requests per second (QPS).

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