Cassandra performance issues after migrating to Lagom 1.6.5

We are trying to migrate from Lagom 1.4.15 to the latest Lagom version 1.6.5 and are using Cassandra (we migrated first to 1.5.1, then to 1.5.5 and then to 1.6.0 and finally 1.6.5).

In our application.conf file, the following value was set:

cassandra-query-journal {
  # Turn off the eventual consistency delay
  eventual-consistency-delay = 200ms

We understand that the recommended minimum value is 2s, but with the above setting, we haven’t experienced any issues and it works fine in our production settings.

After migrating to 1.6.5 we are experiencing performance issues, and overall the system seems to have become very slow. Consequently, a lot of our tests, which depend upon fetching data from read-side tables are failing, which run fine with the 1.4.15 version.

A few questions -

  1. Is this setting being used in the latest Lagom version?
  2. Has the name been changed or the location been changed?
  3. Apart from just the eventual consistency settings, is there anything else which could be causing this slowness?
  4. What (else) can we do to mitigate the performance issues?