Improve core performance

**Feature request**
It would be great to have monitoring for handlers.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_monitoring` with default `false`.

Start by locating the handler implementation and the existing configuration entry points. Check how runtime options are defined and how handler activity is currently surfaced; done means a disabled-by-default enable_monitoring option exists and monitoring behavior is covered for production use.

Written by the indexing model from the issue text.