Maximum sn_ca.add_users.max_users_per_event system property setDetailsThe system property referenced, sn_ca.add_users.max_users_per_event, specifies the maximum number of users the system can add in a single event. We do not recommend increasing the system property to 50K. You should first run a campaign on a test instance with the default settings to observe the performance. If there are more than 1000 users assigned to the campaign, more events will be sent until all users have been added.In the past, our internal testing has demonstrated that the scheduled job, Add Users to Campaigns, completes execution in under 10 minutes with an audience of 100K users in best case scenario.This metric does not cover the full publishing process for a campaign that may have many stages and many items to publish potentially with additional specified delays for specific content.It's not possible to predict the outcome on instance since processing time varies from instance to instance based on its workload. If you observe poor performance, tweak the properties specified here, https://docs.servicenow.com/bundle/sandiego-employee-service-management/page/product/employee-center/reference/properties-installed-with-content-auto.html, Test until you find the right place based on their configuration/load. We recommend first running campaign on a test instance with the default settings to observe the performance. Below is the script to add users to the test instance that might be helpful. It can be run from the Scripts - Background module with an admin account. Script to create 125k users:for (var i = 0; i < 125000; i++) {var x = new GlideRecord('sys_user');x.initialize();var fname = 'test';var lname = 'user' + i;var uname = fname + '.' + lname;var email = uname + '@example.com';x.setValue('first_name', fname);x.setValue('last_name', lname);x.setValue('email', email);x.setValue('user_name', uname);x.setValue('mobile_phone', '+911111111111' + i);x.insert();}