I had this very same question with respect to user metadata. In my use-case the decoration task for logs is quite expensive despite using redis to hold all of my metadata.
In an effort to minimize the load on the decorator (since it's already experiencing load from the current system in place), I thought it would be a good idea to re-index our metadata from scratch into it's own elasticsearch index and then "somehow magically" correlate the user data to a field like userid in elasticsearch.
I'm just not sure what the "somewhat magical" component to this is.
Help would be appreciated! Please let me know if this needs anymore details. The Stackoverflow post is not mine, just referencing.