Design a Ad Serving Service
Last updated: April 29, 2026
Quick Overview
Design a multi-tenant ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Mastercard
System Design
Software Engineer
Mastercard
April 29, 2026Software Engineer
Technical Screen
System Design
Hard
18
9
3,598 solved
Design a multi-tenant ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Mastercard 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
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Consistency models and replication
High-level architecture and component design
API design and rate limiting
Load balancing and horizontal scaling
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 migrate from a monolithic to a microservices architecture?
- What monitoring and alerting would you set up on day one?
- How would you handle a region-wide outage?
- What happens if one of your database nodes goes down?
Practice a Similar Problem on Codemia
Solve a related problem with our interactive workspace, get AI feedback, and view detailed solutions.
Solve on CodemiaSample Answer
Requirements
- Functional Requirements:
- Multi-tenancy support to allow different advertisers to serve ads independently.
- Ability to handle millions of requests per second for ad serving and tracking....
Capacity Estimation
- Traffic Estimation:
- Assume 1 billion impressions per day. That translates to about 11,574 requests per second (1 billion / 86400 seconds).
- With a 10% click-through rate (CTR), we also ...
Submit Your Answer
Markdown supported