When all you have is a hammer, everything looks like a nail

I was supposed to propose a solution for a company that aggregated loan offers from banks, I don't know a better word for it. They wanted an online system for calculating the cost of a loan. Every bank had its own Excel file doing the calculation, protected, so there was no way to see exactly how it was calculated.

So I proposed OLE on a bigger scale. A server with Excel on it, or rather as many Excels as there were banks, the customer enters the amount and the period, we put them into the right cells, Excel calculates, we read the result and show it on the page. Office on a server handling traffic from the internet, what could possibly go wrong :-)

I can picture that server room, a dozen Excels open at once, each pretending to be an application server, and under heavier load one of them asks “do you want to save your changes?” while customers wait for their instalment to be calculated.

To this day I don't know how it could have been proposed better. The Excels were locked, nobody knew the formulas and the banks had no intention of sharing them, so Excel was the only one that knew how to calculate it. When all you have is a hammer, everything looks like a nail, except this time it probably really was a nail.