Design Ad Serving Infrastructure for global users
Last updated: July 23, 2025
Quick Overview
Design a multi-tenant ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Redfin
July 23, 20257
5
4,674 solved
Design a multi-tenant ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Redfin asks this during the Technical Screen to assess your depth in software engineering. They want to see understanding of design patterns, system architecture, and the trade-offs involved in different technical approaches.
What the Interviewer Expects
- Explain the concept clearly with a practical example
- Discuss when and why to apply this principle
- Identify common mistakes and anti-patterns
- Compare with alternative approaches
Key Topics to Cover
How to Approach This
- Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
- Choose data structures based on access patterns, not familiarity.
- Prefer immutable data and message passing over shared mutable state for concurrency.
- Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
- How would you document this for other engineers?
- What testing strategy would you use for this component?
- How would you handle backward compatibility?
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Core Principles
Start by identifying which engineering principles are most relevant: **SOLID Principles**: Single Responsibility (one reason to change), Open/Closed ...
Design Approach
**API Design**: Define clear interfaces before implementation. Use RESTful conventions for HTTP APIs. Version your APIs from the start. Return meaning...
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