Our reverse proxy is supposed to run continously for multiple days or even multiple months. Keeping track of all subject attributes would lead to huge memory consumption, even when the data will never be touched again. Therefore we use a cache system. In the cache every item gets inserted with their maximum life period and gets deleted once this period is over. We use hexadecimal representation of the SHA-256 hash of the access token as key and store the user information and the OpenID Connect Provider. The cache stores the data as CacheItem objects with a minimum heap structure, i.e. the smallest timestamp is on first position. The expire function removes every item from the cache once the timestamp is smaller than the current timestamp, i.e. the CacheItem’s lifetime period is over.