I'm using an API for mutual fund data and right now in my url for the custom data I'm calling data from 2000-1-1 to today. Does anyone know if it downloads from that link one time at the start, or would it make more sense for me to set the date call in the url to only call the day that the backtest is on? Sorry about the confusing wording I was just thinking downloading the full file of 18 years of data each day would be a lot more cumbersome than if it was just downloading one day at a time?