Design a fault-tolerant Payment System

Last updated: September 26, 2025

Quick Overview

Design a fault-tolerant payment system handling millions of requests. Discuss consistency, availability, and performance trade-offs.

Walmart
System Design
Software Engineer
Walmart
September 26, 2025
Software Engineer
System Design Round
System Design
Easy

791

12

2,293 solved


Design a fault-tolerant payment system handling millions of requests. Discuss consistency, availability, and performance trade-offs.

How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
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Sample Answer
Requirements
  • Functional Requirements:
    • Process payment transactions for purchases made in-store and online.
    • Support multiple payment methods (credit/debit cards, digital wallets, gift cards).
    • Impl...
Capacity Estimation

To estimate the capacity needed for the payment system:

  • User Base: Assume 50 million active users.
  • Transaction Rate: Assume an average of 5 transactions per user per day.
  • Peak Load: ...

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