Design an automated email marketing system
to send emails to a target audience of 1 million people without slowing down user login processes.
About this question
Category
System Design
Subcategory
Asynchronous & Communication
Difficulty
Easy
Est. time
40 min
What this question helps you practice
This system design prompt tests whether you can send a large marketing campaign without degrading core user flows. A strong answer should separate campaign processing from login, respect deliverability and compliance constraints, and include throttling, retries, and monitoring.
How to practice
Clarify campaign requirements
Ask about audience segmentation, personalization, send window, provider limits, compliance, and metrics.
Design the pipeline
Use campaign service, recipient snapshot, queue workers, template rendering, provider, and event tracking.
Protect core systems
Isolate login traffic, throttle sending, handle retries, respect unsubscribe, and monitor failures.
Strong answer signals
Uses queues and worker pools to control throughput instead of one massive synchronous job.
Separates campaign data access from authentication and login critical paths.
Covers unsubscribe, bounce handling, provider rate limits, and delivery analytics.
Common mistakes
Sending emails directly from the login or request path.
Ignoring email provider limits, spam risk, or unsubscribe compliance.
Retrying failures blindly and causing duplicate emails or provider throttling.
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