Design a low-latency Payment System

Last updated: December 21, 2025

Quick Overview

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

Walmart
System Design
Machine Learning Engineer
Walmart
December 21, 2025
Machine Learning Engineer
Onsite
System Design
Easy

129

11

3,989 solved


Design a low-latency 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

  1. Process Payments: Allow users to make payments using various methods (credit/debit cards, digital wallets, etc.).
  2. Transaction History: Users should be able to...
Capacity Estimation

Assuming Walmart has around 250 million unique customers and that on average, 10% of them make a payment in a day:

  • Daily Transactions: 250 million * 10% = 25 million transactions.
  • **Peak Load ...

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