Based on the Icon the process group I think the it's is a Microsoft SQL Server.
You probably encountered a higher load for the SQL as expected. If you have your application deep monitored with Dynatrace, you can investigate the SQL statements issued. Even without deep monitoring, you can investigate the network traffic to/from the MSSQL process or the MSSQL metrics to see if there was a higher load.
The only way to drill down the windows system process group is to get the support archive and browse the processesSnapshot.log which processes belong to the group.
Windows System includes core windows processes and also kernel processes.
In your case, it might be just a heavily increased IO due to some database activity.