What the best way to launch the rule engine

Hi !
I'm new to rules engine and json-rules-engine particulary …

I need to apply rules on iot metrics to launch alert through mail, sms, etc …
I have a rules editor in a Vuejs frontend with write the json rules in a postgressql database through a graphql API.

What is the best way to scan my metrics time series table ? Launch rules on insert or with a cron ?

Thanks for your help