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Quick Question with External Data Source

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?

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GetSource instructs LEAN where to find your data and it returns an object containing the string Url to find your data, and the format of the data. When the URL changes the data is downloaded again. This allows LEAN to cache large files and only download new data when requested. The Reader will then take each line and create the custom object. So it would make sense to download all the data at once and read it than calling the API everyday.

https://www.quantconnect.com/docs/algorithm-reference/importing-custom-data
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Perfect, thank you!

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