EntityRepository.php

    final public function findReadOnly($id, $fetchMode = self::FETCH_LAZY_MODE)
    {
        // initialize answer
        $res = null;

        // calculate key
        $cacheKey = self::getCacheKey($this->getEntityName(), $id, $fetchMode);

        // check cache
        if (($cacheRes = $this->fetchFromCache($cacheKey)) !== false) {
            // cache hit
            $res = $this->getEntityManager()->merge($cacheRes);

            // just for debug purposes
            if ($this->logger instanceof LoggerInterface) {
                $this->logger->debug('Find read only entity cache hit ' . $cacheKey);
            }
        } elseif (is_object($dbRes = $this->findReadOnlyDb($id, $fetchMode))) {
            // store into cache
            $this->storeIntoCache(
                $cacheKey,
                $dbRes,
                $this->getExpiration($fetchMode)
            );

            $res = $dbRes;
        }

        return $res;
    }