I would love to use a CDN. But I am afraid of things I do not fully understand, and I am afraid of making things too complex. If I update a single file, how lo

I would love to use a CDN. But I am afraid of things I do not fully understand, and I am afraid of making things too complex. If I update a single file, how long it takes until nobody in the world can access the old version anymore? Does it take seconds / minutes / hours? Also, some files should not be cached at all (like PHP requests). I am afraid it would take me days or weeks to learn everything and to cofigure the CDN properly, and I am risking being offline for a part of the world during that time. Also, if there is a problem at the CDN, my website would be broken, too. If someone could help me, you can write me at support@photopea.com