bidirectional xdcr elasticsearch and couchbase
as far as I know it's currently not possible to sync changes from Elasticsearch to Couchbase.From a semantic perspective, you probably don't want to change an index, and forward a change from the index to the DB backing that index.
I maintain the Couchbase transport plugin and as Laurent answered earlier, it doesn't allow replicating from Elastic back to Couchbase. While it's technically possible to implement this functionality, it wouldn't make sense to do so in practice. The whole point of replicating to Elastic is to use it as an index on top of your source of truth, which is Couchbase. That way you get the high performance reads and writes of Couchbase and the query and search functionality of Elastic. Replicating changes back to Couchbase would mean the data there is no longer authoritative, which in turn opens the door to all sorts of concurrency and data integrity problems.