Design Ride Matching Infrastructure for mobile apps
Last updated: September 11, 2025
Quick Overview
Design a distributed ride matching system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Plaid
System Design
Software Engineer
Plaid
September 11, 2025Software Engineer
Onsite
System Design
Medium
114
10
2,417 solved
Design a distributed ride matching system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Plaid asks this during the Onsite to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.
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
Load balancing and horizontal scaling
Requirements gathering and capacity estimation
Security and authentication
High-level architecture and component design
Consistency models and replication
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 optimize costs as the system scales?
- What happens if one of your database nodes goes down?
- How would you handle schema migrations with zero downtime?
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Requirements
Functional Requirements
- User Registration and Authentication: Users must be able to create accounts, log in, and authenticate securely.
- Ride Request Submission: Users can submit ride...
Capacity Estimation
Back-of-Envelope Calculations
- Estimated Daily Active Users: Assume 1 million active users per day.
- Average Requests per User: Each user makes approximately 5 ride requests a day.
- **T...
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