We're having some constants declared to define Elasticsearch configuration properties, which currently expect a single global value, for example (but not only):

To be consistent with the other configuration properties, these should rather be parsed independently on a per-backend base.
So the constants would only define the post-fix, and we'd document as valid configuration options properties like:

This would imply that we want to support using multiple Elasticsearch clusters, which is currently not a given and should be discussed first.

Even if we want to support a single Elasticsearch cluster, scoping the INDEX_MANAGEMENT_STRATEGY is probably a good idea.