Hi,

A Scheduled Job can do your work. Try with the below one.

var ka = new GlideRecord('kb_knowledge');
ka.query();
while(ka.next())
{
var exp = new GlideDateTime(ka.exp_date).getDate(); //Considered exp_date as Article Expiry Date
if(exp.addDaysUTC(7)==new GlideDateTime().getDate())
{
gs.eventQueue('your_event_name',ka,gs.getUser()); //Include the recepients you require
}
}

//Running this Scheduled Job daily will send notification 7 days before the ExpiryDate
//You have to create a notification to be triggered when 'your_event_name' is triggered

Hope this helps!

Thanks,

Archana