Innovations in the area of server-side processing when committing transactions to disk in a distributed database system can improve computational efficiency at database nodes and/or reduce network bandwidth utilization. For example, when transactions are committed in a database system, at a master node of the database system, a server uses different threads for certain processor-intensive operations and certain I/O-intensive operations. Or, as another example, when transactions are committed in a database system, at a master node of the database system, a server groups jobs for I/O requests.