You didn't mention when was the last time you ran `nodetool repair` (or using Scylla Manager to run repair) on this cluster. ScyllaDB (as well as Cassandra) uses eventual consistency, which means your write request will be satisfied when the Consistency level (CL) of that request was achieved. If you used CL=ONE for your writes, than only 1 replica needs to ACK for the application to consider this successful. The replication to the 2nd replica will be done a-synchronically (and can also fail for various reasons). Here comes the anti-entropy mechanism, which you can read more about them here: https://docs.scylladb.com/architecture/anti-entropy/ You must make sure your cluster completed cluster wide repair before the table's `gc_grace_seconds` value (default 10 days) You should have also fully repaired your cluster before adding the 2nd DC, or at least done it after you've added the 2nd DC. This is also written in our docs.

Context: Stack Overflow #72934006 (accepted answer, 7 votes): I am using Scylla version 4.6.3. I have a cluster of 3 nodes in a single DC. I have followed the instructions given in https://docs.scylladb.com/operating-scylla/procedures/cluster-management/add-dc-to-existing-dc/ to add 3 new nodes in a new DC. After the nodes in the new DC are started, I check nodetool status and ensure all are up and running. Now since all nodes are part of the same cluster, I assume the query results should be the same irrespective of which node I run the cql query on, isn't it? But I see that the data is different when the query is run on different nodes. In fact the...