Design a Search Service
Last updated: January 21, 2026
Quick Overview
Design a geo-distributed search system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Visa
January 21, 202613
15
3,955 solved
Design a geo-distributed search system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Visa 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
- What happens if one of your database nodes goes down?
- How would you handle schema migrations with zero downtime?
- How do you ensure data consistency across multiple services?
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Requirements
Functional Requirements
- Search Functionality: Users can perform searches based on keywords, geographic location, and transaction types (e.g., payment, withdrawal).
- Real-time Updates:...
Capacity Estimation
To estimate the capacity, we can make some back-of-envelope calculations:
- User Base: Assume Visa has 100 million users globally.
- Search Requests: If 10% of users search once a day, that'...
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