The Clear Cache API evicts users from the user cache. You can completely clear the cache or evict specific users.

For example, to evict all users cached by the file realm:

POST _xpack/security/realm/default_file/_clear_cache

To evict selected users, specify the usernames parameter:

POST _xpack/security/realm/default_file/_clear_cache?usernames=rdeniro,alpacino

To clear the caches for multiple realms, specify the realms as a comma-delimited list:

POST _xpack/security/realm/default_file,ldap1/_clear_cache

For more information, see Controlling the User Cache.