As a Jira Administrator you can set an upper limit for issue creating solution.
Meaning, in Jira add-on section you can switch on bulk issues creation and an upper limit after exceeding which issues will be created by bulk solution. In other cases issues will be created in ordinary manner one by one.
It is turned off by default:
You can easily turn it on and change default value, if you creating lots of issues using Excel Connector you can decrease this value and check how it affects Jira performance
This feature will be improved over time, as it could heavily increase performance.