Architect a multi-tenant Feed Generation Engine
Last updated: July 29, 2025
Quick Overview
Design a multi-tenant feed generation system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
PayPal
July 29, 20251
12
329 solved
Design a multi-tenant feed generation 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
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 handle a region-wide outage?
- How do you ensure data consistency across multiple services?
- What happens if one of your database nodes goes down?
- How would you handle a 10x increase in traffic overnight?
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Requirements
Functional Requirements:
- Multi-Tenancy: Support multiple tenants (e.g., businesses) generating and consuming feeds independently.
- Feed Generation: Generate personalized feeds based o...
Capacity Estimation
Assuming PayPal serves approximately 300 million active users:
- If each user generates an average of 5 feed requests per day, that results in:
- Daily Feed Requests: 300M users * 5 requests/use...
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