When to use it
Use it when the interviewer asks if you have questions. Always have at least one ready. Asking what success looks like early on shows you're thinking about doing the job well, and the answer tells you what they'll expect.
Example
Interviewer: “Any questions for me?”
You: “What would success look like in the first 90 days?”
Interviewer: “Getting the reporting process running smoothly.”
In an email or Slack message
Write down two or three questions before the interview. Other good ones: “What's the biggest challenge for this team right now?” and “How do you like updates from your team?”