An alternative to transient and object-cache

wp-meta_cache.php

$cache_key = '_ssr-schedule';
$cache = get_post_meta( $frag_ID, $cache_key, true );
if ( empty( $cache ) || $cache['expires'] < time() ) {
	$var = '[path]';
	$url = '[path]' . $var;
	$request  = wp_remote_get( $url, array( 'timeout' => 120, ) );

	if( is_wp_error( $request ) ) { return false; }
	$response = wp_remote_retrieve_body( $request );
	$data     = json_decode( $response, true ); // `true` translate into an array instead of an object
    $cache = array(
        'expires' => time() + 24 * HOUR_IN_SECONDS,
        'data' => $data,
    );

    update_post_meta( $post->ID, $cache_key, $cache );
}

$data = $cache['data'];