You might want to check out the release notes of 7.23.15 : https://docs.mendix.com/releasenotes/studio-pro/7.23#72319
Furthermore you should upgrade to 7.23.19 at least because of vulnarability issues in version prior to this one.
Regards,
Ronald
A drastic measure would be only to allow 1 session per user.
https://docs.mendix.com/refguide/project-settings#multiple-sessions
But what you actually might be looking for is an API manager/ESB with rate limiting capabilities.