Design a scalable Payment System
Last updated: May 7, 2026
Quick Overview
Design a scalable payment system handling millions of requests. Discuss consistency, availability, and performance trade-offs.
Walmart
System Design
Software Engineer
Walmart
May 7, 2026Software Engineer
System Design Round
System Design
Medium
245
9
4,176 solved
Design a scalable payment system handling millions of requests. Discuss consistency, availability, and performance trade-offs.
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.
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Practice System Design ProblemsSample Answer
Requirements
Functional Requirements
- Transaction Processing: The system must handle payment transactions securely and reliably, supporting various payment methods (credit/debit cards, digital wallets, e...
Capacity Estimation
Back-of-Envelope Calculations
- Expected Transaction Volume: Assume Walmart has 250 million customers. If 10% make a purchase daily, that's 25 million transactions.
- Peak Load: During pea...
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