Design a distributed Ad Serving System
Last updated: March 17, 2026
Quick Overview
Design a distributed ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Mastercard
March 17, 2026452
4
2,155 solved
Design a distributed ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Mastercard asks this during the Technical Screen 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
- Clearly define functional and non-functional requirements
- Propose a reasonable high-level architecture with core components
- Choose appropriate data storage solutions with basic justification
- Discuss basic scaling strategies (horizontal scaling, caching)
- Identify potential bottlenecks and suggest simple solutions
Key Topics to Cover
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
- What monitoring and alerting would you set up on day one?
- How would you handle a region-wide outage?
- How would you handle schema migrations with zero downtime?
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Requirements
Functional Requirements
- Ad Request Handling: The system should handle millions of ad requests per second from various clients.
- Ad Personalization: Serve personalized ads based on use...
Capacity Estimation
Assuming Mastercard serves ads to approximately 500 million unique users a month, and each user generates about 10 ad requests per day:
- Daily Requests: 500 million users * 10 requests = 5 billi...
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