Keeping coffee refrigerated does not actually help it stay fresher. It does introduce moisture though which will negatively affect the coffee.
It is recommended that you brew the coffee with a few minutes of grinding. Otherwise you lose some of the aromatics and oils.
My espresso machine grinds just enough for a single or double shot of espresso directly into the portafilter.
The extremely fine, powdery grind used for espresso would not be appropriate for cold brew. You would want a medium to coarse grind similar to French press.
I still have my Bodum burr grinder that could grind beans appropriate for cold brew, but again, they quickly degrade.
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