TL;DR - it's for alerting on ELK, claimed to come with a better query language than both SPL and Elastic QueryDSL (for the use case at least), and a decent admin UI for managing the queries.
https://github.com/etsy/411/blob/master/docs/GettingStarted....
Looks like this wasn't ready to be released? The domain also just points to the github repo.
TL;DR - it's for alerting on ELK, claimed to come with a better query language than both SPL and Elastic QueryDSL (for the use case at least), and a decent admin UI for managing the queries.