Is the SMVI domain account also the same user's credentials that are registered at https://VSC_SERVER:8143/Register.html? If so, the 15s interval is likely caused by Optimization and Migration polling for virtual machine events. Unfortunately, this is not currently easily configurable. If you aren't using Optimization and Migration, you can disable Optimization and Migration by moving VSC_INSTALL_DIR\subplugins\deploy\caster.war outside of the subplugins\deploy directory or renaming it so that it does not end with ".war".