Design
Digital Wallet (Single Currency)
Design a digital wallet system supporting deposits, withdrawals, and balance tracking with a full transaction history.
01 - Why interviewers ask this
Money-handling problems are popular specifically to test rigor — interviewers want to see an immutable transaction ledger and real concurrency safety, not a single mutable balance field.
02 - Where this system exists in the real world
You interact with this design every day.
Digital wallets (Paytm, Google Pay, PayPal balance)
In-app currency / credits systems
Prepaid card balance management
03 - What you'll master
Solve this once. Know it forever.
Model money as an append-only transaction ledger
Prevent overdraft under concurrent access
Keep balance derivation auditable and consistent
04 - What you'll design
6 functional · 2 non-functional requirements.
Create a wallet for a user with zero starting balance
5 more requirements inside
Sign in to unlock the full brief and start designing
05 - Companies that ask this
You may face this exact question in your next interview.
Ready?
Open the canvas.
Design it yourself.
See all requirements, use staged hints, run your code, and compare with community discussions - all on the same canvas.
Start Solving