Build a geo-distributed Ad Serving Pipeline
Last updated: August 3, 2025
Quick Overview
Design a geo-distributed ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
DoorDash
August 3, 20259
4
2,117 solved
Design a geo-distributed ad serving system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
DoorDash 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
- Design a complex system component applying multiple engineering principles
- Reason about system-level trade-offs: performance, reliability, developer experience
- Discuss advanced patterns: event sourcing, CQRS, distributed transactions
- Address cross-cutting concerns: observability, security, backward compatibility
- Demonstrate depth in both theoretical foundations and practical implementation
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
- What are the security implications of this design?
- How would you handle backward compatibility?
- How would this design change if the team size doubled?
- How would you document this for other engineers?
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
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...
Submit Your Answer
