Splitwise System Design:

Detailed Designing of Splitwise System

Use Cases to be covered:

User should be able to add expense
User should be able to enter the expense he paid for friends and the amount should be split amongst friends.
The Splitting of expense is of the following types:
- Split Equally : This case should handle the edge cases like recurring decimal digits like 100/3 =33.33333...333 in optimised way
- Split Unequally :
  - User should be able to add the exact amount pertaining to every expense. The sum total of the amounts entered should match the total amount spent by the user.
  - User should be able to have option for percentage wise splitting. The sum total of the percentages should be equal to 100%.
Multiple users can pay for an expense.
Groups can be created and people can be added to the group.
The expenses can be group wise or non-group wise
User should be able to see the net balance in the total section and also against each friend.
The expenses added should have the details like name, date, image, location, category etc.
Settlement of expenses can be of 2 types- Partial and Final Settlement. User should be able to view and manage both
User should be able to see all transaction histories.
User should be provided with an option to enable Simplify Debt.
- The Simplify Debt optimises the transaction exchanges. For example, If A owes B $10 and B owes C $10, then A can directly pay C $10.

System should be available to everyone at all times
System should be consistent and show accurate results
System should handle heavy request flows since many users can login to the system at same time
System should be secure