A great high-scale customer service rep; once asked, "How do you scale what you do?"
Should answer with the following key ideas...
Tools (Ticket management etc)
Playbooks (To drive consistency and improve quality over time)
Knowledge-base articles (To mitigate tickets in the first place)
Product Feedback/fixes (To eliminate product defects that cause confusion)
If they answer with ideas in the last category, they're a unicorn. Hire them immediately.