Source

File: wp-includes/ms-functions.php

function wp_is_large_network( $using = 'sites', $network_id = null ) {
	$network_id = (int) $network_id;
	if ( ! $network_id ) {
		$network_id = get_current_network_id();
	}

	if ( 'users' === $using ) {
		$count = get_user_count( $network_id );
		/**
		 * Filters whether the network is considered large.
		 *
		 * @since 3.3.0
		 * @since 4.8.0 The `$network_id` parameter has been added.
		 *
		 * @param bool   $is_large_network Whether the network has more than 10000 users or sites.
		 * @param string $component        The component to count. Accepts 'users', or 'sites'.
		 * @param int    $count            The count of items for the component.
		 * @param int    $network_id       The ID of the network being checked.
		 */
		return apply_filters( 'wp_is_large_network', $count > 10000, 'users', $count, $network_id );
	}

	$count = get_blog_count( $network_id );

	/** This filter is documented in wp-includes/ms-functions.php */
	return apply_filters( 'wp_is_large_network', $count > 10000, 'sites', $count, $network_id );
}