src/Neutrino/Cache/CacheStrategy.php
public function exists($keyName = null, $lifetime = null)
    {
        return $this->uses()->exists($keyName, $lifetime);
    }
public function exists($keyName = null, $lifetime = null)
    {
        return $this->uses()->exists($keyName, $lifetime);
    }
Checks if cache exists and it hasn't expired

@param string $keyName
@param int    $lifetime

@return boolean