We have an important announcement for users running Temporal versions < 1.6.0 on Cassandra persistence. Before 1.6.0 there was a bug which could cause workflows to be started without creating an initial event, leaving them dangling and unaccessible. This bug only occurs when Cassandra returns an error during creation of the initial event, which is not common for most workloads. That being said, making changes to your existing Cassandra deployment (adding nodes and anything which affects the ring) will significantly increase the chance of encountering the bug. For this reason we highly recommend that all Temporal-Cassandra users immediately upgrade to 1.6.0 or higher and refrain from making changes to their Cassandra cluster until they’ve upgraded.
Edit: As an update, we have decided that we will backport the bug fix to all previous minor (1.x) versions. This way users will not feel forced to rush an upgrade.