title: How to read from Kafka and Query from an external store like Cassandra in Spark Structured Streaming?
body: <p>How to read from Kafka and Query from an external store like Cassandra in Spark Structured Streaming?</p>
  
  <p>I get stream of messages from Kafka and I would like to apply Map operation on it and for each key I would like to query a datastore like Cassandra and get more information for that key and apply further operations on the stream. How do I do that using Spark Structured Streaming 2.2.0?</p>