San Cirano Payments
Dues and payments for the club in one place, so tracking them stopped living in somebody's spreadsheet.
TODO: open with the problem, and be concrete about the mess. Who was chasing what, in which spreadsheet, and how often it was wrong.
What it handles
TODO: the scope. Who pays, how often, what happens when they don't, and who needed to see it.
Getting money right
TODO: this is the part that makes it a real engineering write-up. Money has no forgiving failure mode — a stat can be re-entered, a payment recorded twice cannot be waved away. What did you do to make the wrong state unreachable rather than merely unlikely?
What I'd do differently
TODO: be specific and be honest.