Couchbase Eventing Service provides a framework for writing your own functions to process data change events (create, update, delete/expiry). Couchbase Server 6.5 introduces a set of important improvements to the Eventing Service that enables a lot of new use cases and simplifies maintenance of Eventing Functions.
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Source Bucket Mutations
An Eventing function is defined to listen to the changes of one bucket, known as the source bucket of the function. Previous versions of Couchbase did not allow a function to mutate documents in its source bucket, because if these mutations are being fed back to the function, it can potentially create an infinite recursion. This limitation is removed in Couchbase 6.5: an Eventing function can now change the documents on the source bucket, even the document of the change event. Couchbase makes such changes safe by suppressing their recursive propagation to the same Eventing function.