There are several important fixes that went in to RMB specially in release 27.1.2 but this module uses an older version 26.4.2. Also, noticed that this module hasn't been released for Q4. Updating RMB dependency will solve many memory related issues with this module.
How to upgrade (recipe): https://github.com/folio-org/raml-module-builder/blob/master/doc/upgrading.md
See the heap dump attached. It shows codehale doprwizard metrics and asyncpostgressql connections - which was fixed in RMB 27.1.2.
(Per Slack message from Sobha, this was noticed by the EBSCO FOLIO hosting FOLIO staff. They noticed an issue with performance of mod-feesfines. Specifically they noticed a memory leak.)