Access external data for enriching or use in checks

I’m currently playing around with Sensu and trying to work out how to achieve two specific requirements:

1 - Route alerts using external reference data

2 - Enrich alerts using external reference data

Assuming we have multiple systems that master different domains, what’s the best way for Sensu to tap into this rich data to use in a filter, check or a handler?

Any direction on an recommended approaches would be greatly appreciated!