Can "keys_zone" be set as zero and "inactive" parameter disabled when nginx used as a cache reverse proxy ?

Issue

• Can keys_zone be set as zero and inactive parameter disabled when nginx used as a cache reverse proxy ?
• Is there a way to specify a keys_zone size as 0 when nginx used as a cache reverse proxy serve looking at the proxy_cache_path directive ?
• Is there a way to disable the inactive parameter when nginx used as a cache reverse proxy server looking at the proxy_cache_path directive ?