Feed, RSS not able to clear the cache and cannot change the limit of cache life time

The WordPress Feed system is EXTREMELY complex for no reason.

I have been going around and around and around in circles.

I am using:

function do_not_cache_feeds(&$feed) {
    $feed->enable_cache(false);
}
add_action( 'wp_feed_options', 'do_not_cache_feeds' );

define( 'MAGPIE_CACHE_AGE', 1 );

function prefix_set_feed_cache_time( $seconds ) {
    return 1;
}
add_filter( 'wp_feed_cache_transient_lifetime' , 'prefix_set_feed_cache_time' );

In my functions.php file in my themes folder.

Did not work for a reason that is beyond me.

So first questions is: Is there any way I can get rid of the caching of the feed? I am already using Varnish?

Second, for the current cached feeds how can I clear them?

Third, where the hell are they been stored? I literally look everywhere.

Solutions Collecting From Web of "Feed, RSS not able to clear the cache and cannot change the limit of cache life time"

If you are using W3 Total Cache or any other caching system make sure it does not cache the feeds.

WordPress uses SimplePie for parsing it’s feeds. They are many things that are happening at the same time that can cause some confusion. First SimplePie does cache the feeds, I haven’t figured yet how to clear it or where it is stored. But you can use this code to force it to not cache it or cache the feeds for a shorter time.

function do_not_cache_feeds(&$feed) {
    $feed->enable_cache(false);
}
add_action( 'wp_feed_options', 'do_not_cache_feeds' );

function prefix_set_feed_cache_time( $seconds ) {
    return 1;
}
add_filter( 'wp_feed_cache_transient_lifetime' , 'prefix_set_feed_cache_time' );

Also when testing make sure you clear your browser cache. Because SimplePie with WordPress uses HTTPCG (HTTP Conditional Get). For more details about SimplePie caching go here: SimplePie caching.