Reactive streams java

I want to listen to a changestream for a collection , which java driver should I use ,

  1. mongo async driver
  2. mongo sync driver

You can use either of the two:

Also note that from the MongoDB Reactive Streams Java Driver Documentation:

The Reactive Streams Driver is the canonical asynchronous Java driver for MongoDB, providing asynchronous stream processing with back pressure in line with the Reactive Streams specification. The API mirrors the now-deprecated callback-based MongoDB Async Driver.