==================================================== How does ScyllaDB LWT Differ from Apache Cassandra ? ==================================================== ScyllaDB is making an effort to be compatible with Cassandra, down to the level of limitations of the implementation. How is it different? * ScyllaDB most commonly uses fewer rounds than Cassandra to complete a lightweight transaction. While Cassandra issues a separate read query to fetch the old record, scylla piggybacks the read result on the response to the prepare round. * ScyllaDB will automatically use synchronous commit log write mode for all lightweight transaction writes. Before a lightweight transaction completes, scylla will ensure that the data in it has hit the device. This is done in all commitlog_sync modes. * Conditional statements return a result set, and unlike Cassandra, ScyllaDB result set metadata doesn’t change from execution to execution: ScyllaDB always returns the old version of the row, regardless of whether the condition is true or not. This ensures conditional statements work well with prepared statements. * For batch statement, the returned result set contains an old row for every conditional statement in the batch, in statement order. Cassandra returns results in clustering key order. * Unlike Cassandra, ScyllaDB uses per-core data partitioning, so the RPC that is done to perform a transaction talks directly to the right core on a peer replica, avoiding the concurrency overhead. This is, of course, true, if ScyllaDB’s own shard-aware driver is used - otherwise we add an extra hop to the right core at the coordinator node. * ScyllaDB does not store hints for lightweight transaction writes, since this is redundant as all such writes are already present in system.paxos table. More on :doc:`Lightweight Transactions (LWT) `