Update request processor (URP) and field transformer (FIT)

DataStax recommends using a field input/output transformer (FIT) API with DataStax Enterprise (DSE):

The DSE custom URP implementation isn’t recommended because it is almost always unnecessary. DSE custom URP provided similar functionality to the Apache Solr™ URP chain, but appeared as a plugin to Solr. The classic URP is invoked when updating a document using HTTP and the custom URP is invoked when updating a table using DSE. If both classic and custom URPs are configured, the classic version is executed first. The custom URP chain and the FIT API work with CQL and HTTP updates. The field input/output transformer, an alternative for handling update requests, is executed later than a URP at indexing time.