SingleStore DB

Does being in-memory mean that SingleStore DB will lose all data upon system failure or restart?

No. Unlike traditional relational database management systems, SingleStore DB uses RAM as the primary storage for data. However, SingleStore DB continuously backs up data to disk with transaction logs and periodic snapshots. These features can be tuned all the way from synchronous durability (every write transaction is recorded on disk before the transaction completes) to purely in-memory durability (maximum sustained throughput on writes).

On restart, SingleStore DB uses the snapshot and log files to recover its state to what it was before shutting down. Because the recovery process is parallelized across CPUs, the bottleneck in this process is the sequential hard drive speed.

See Replication and Durability for more information.