Design Payment Infrastructure for mobile apps
Last updated: March 10, 2026
Quick Overview
Design a real-time payment system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Coinbase
March 10, 202673
13
4,070 solved
Design a real-time payment system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Coinbase 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
- Clearly define functional and non-functional requirements
- Propose a reasonable high-level architecture with core components
- Choose appropriate data storage solutions with basic justification
- Discuss basic scaling strategies (horizontal scaling, caching)
- Identify potential bottlenecks and suggest simple solutions
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 would the deployment pipeline look like for this system?
- How would you migrate from a monolithic to a microservices architecture?
- What happens if one of your database nodes goes down?
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
Requirements
Functional Requirements
- Real-time Payment Processing: The system must process transactions instantly, providing real-time feedback to users.
- Multi-Currency Support: Users should be a...
Capacity Estimation
To estimate capacity, assume the following:
- User Base: 10 million active users.
- Transactions per User: On average, 5 transactions per user per day.
- Peak Load: 20% of transactions occ...
Submit Your Answer
