How to check file existence in htaccess?

Good afternoon, dear Habraludi!

There was a question in which Google so far could not help me. Is it possible to check for the existence of a file through htaccess? :) That is, is there any non-standard RewriteCond for such an operation? :)

The goal is to check whether the file has been cached on the server and, if so, not to redirect to index.php, if not, to redirect and create the cache ...
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I thought about 404 and the usual rewrite (for example, when requesting / blog / bla-bla / redirect to / cache / blog / bla-bla / without changing the URL, and in the case of 404 - returning to index.php), only I think what will be the incomplete cycle with this option ...