This is an obvious point for most of you, but Google's John Mueller explained on Twitter that even if a page isn't in Google's cache, it can still rank just as well as other pages.
He wrote, "pages can rank without an accessible cache, that can happen & isn't a sign that something's broken."
@jackstonehouse pages can rank without an accessible cache, that can happen & isn't a sign that something's broken.
— John Mueller (@JohnMu) June 20, 2016
You can specifically tell Google not to cache your pages by using the noarchive meta tag or you can file a removal request and select the "Remove page from cache only" option.
Again, this won't stop Google from indexing and ranking your pages.
Forum discussion at Twitter.