Design a large-scale Content Delivery Platform
Last updated: August 6, 2025
Quick Overview
Design a geo-distributed content delivery system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
PayPal
System Design
Software Engineer
PayPal
August 6, 2025Software Engineer
System Design Round
System Design
Medium
39
6
2,177 solved
Design a geo-distributed content delivery system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at PayPal 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
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
Failure handling and fault tolerance
Partitioning and sharding strategies
Database selection and data modeling
Requirements gathering and capacity estimation
Caching strategies (local, distributed, CDN)
API design and rate limiting
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 do you ensure data consistency across multiple services?
- How would you implement rate limiting to protect the system?
- How would you optimize costs as the system scales?
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Requirements
Functional Requirements:
- Content Delivery: Serve static and dynamic content (images, videos, documents) with low latency.
- Geo-Distribution: Content should be available from multiple ...
Capacity Estimation
User Base and Traffic Estimation:
- Users: Assume 100 million active users with an average of 5 requests per user per day.
- Total Requests: 100 million users * 5 requests = 500 million re...
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