Low-Level Design rounds at Paytm center on real payments-domain systems — wallets, transfers, and account linking — where interviewers expect you to drive requirement clarification yourself before touching a class diagram, then justify every design-pattern choice rather than just naming one.
Problem 1Design a UPI-like Digital Wallet & Payments System
Design a system that supports multiple wallet types for a user, lets a user link one or more bank accounts, transfer money to other users, check balances, and retrieve transaction history.
Requirements to clarify first
- Which wallet types exist (a plain prepaid wallet, a KYC-limited 'mini' wallet, a cashback/rewards wallet) and can one user hold several at the same time?
- Does a transfer move money only wallet-to-wallet, or can the source be a linked bank account and the destination another user's bank account (UPI-style)?
- What must hold if a transfer fails halfway — is a debit without a matching credit ever acceptable, and how long does the user wait before a reversal?
More LLD prompts asked at fintech/payments companies
The class design, entity list, design-pattern reasoning and follow-up discussion for these — plus the full worked solution above — are part of the Placement-Ready PYQ Kit.
2 more LLD prompts with full class designs in the full Placement-Ready PYQ Kit