_global_groups( $groups ) {
		if ( ! is_array( $groups ) ) {
			$groups = array( $groups );
		}

		foreach ( $groups as $group ) {
			$cache = $this->_get_engine( $group );
			$cache->add_global_groups( array( $group ) );
		}
	}

	/**
	 * Adds non-persistent cache groups to the cache engine.
	 *
	 * @param mixed $groups An array or string of cache groups to add as non-persistent.
	 *
	 * @return void
	 */
	public function add_nonpersistent_groups( $groups ) {
		if ( ! is_array( $groups ) ) {
			$groups = array( $groups );
		}

		foreach ( $groups as $group ) {
			$cache = $this->_get_engine( $group );
			$cache->add_nonpersistent_groups( array( $group ) );
		}
	}

	/**
	 * Retrieves the appropriate cache engine based on the group.
	 *
	 * @param string $group The cache group.
	 *
	 * @return object The cache engine for the specified group.
	 */
	private function _get_engine( $group = '' ) {
		if ( isset( $this->_cache_by_group[ $group ] ) ) {
			return $this->_cache_by_group[ $group ];
		}

		return $this->_default_cache;
	}

	/**
	 * Decreases the cached value of a given ID by a specified offset.
	 *
	 * @param string $id     The cache key.
	 * @param int    $offset The value to decrease by.
	 * @param string $group  The cache group.
	 *
	 * @return mixed The updated value if successful, otherwise false.
	 */
	public function decr( $id, $offset = 1, $group = 'default' ) {
		$cache = $this->_get_engine( $group );
		return $cache->decr( $id, $offset, $group );
	}

	/**
	 * Increases the cached value of a given ID by a specified offset.
	 *
	 * @param string $id     The cache key.
	 * @param int    $offset The value to increase by.
	 * @param string $group  The cache group.
	 *
	 * @return mixed The updated value if successful, otherwise false.
	 */
	public function incr( $id, $offset = 1, $group = 'default' ) {
		$cache = $this->_get_engine( $group );
		return $cache->incr( $id, $offset, $group );
	}

	/**
	 * Switches to a different blog context in a multisite environment.
	 *
	 * @param int $blog_id The blog ID to switch to.
	 *
	 * @return void
	 */
	public function switch_to_blog( $blog_id ) {
		foreach ( $this->_caches as $cache ) {
			$cache->switch_blog( $blog_id );
		}
	}
}