This was a financial function which calculated an internal return of return for a long series of uneven cash flows, essentially a python implementation of the X

This was a financial function which calculated an internal return of return for a long series of uneven cash flows, essentially a python implementation of the XIRR function that spreadsheets have. To get to the required two decimal places of precision, each call would recurse 50-60 or more times so this was more or less all that the server was doing. A VERY low hanging fruit.