Design
Splitwise / Expense Splitter
Design an expense splitting app where groups of users can track shared expenses, split costs, and settle debts.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
It's one of the most-asked LLD questions in industry interviews specifically for the "debt simplification" algorithm — it reveals whether you can go beyond CRUD into a genuine graph/greedy algorithm.
02 - Where this system exists in the real world
You interact with this design every day.
Splitwise / group expense-sharing apps
Roommate and trip expense trackers
Corporate expense reimbursement splitting
03 - What you'll master
Solve this once. Know it forever.
Model group expenses and individual balances
Implement a debt-simplification algorithm
Support multiple split strategies (equal, %, exact)
04 - What you'll design
7 functional · 4 non-functional requirements.
Users create groups (trips, households, friends)
6 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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