Crowd freezes under heavy load

This is related to CWD-3692 .

Crowd has database lockups under significant load. It appears to be related to locking of the cwd_token table by an insert or delete statement. Crowd appears to use up its database connections and thus become unresponsive. I have updated that ticket with comments which document the queries in question that hang:

https://jira.atlassian.com/browse/CWD-3692?focusedCommentId=561387&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-561387