On-call
A rotation where one developer is the designated responder if the team's live software breaks, including at night.
What it tells you about a developer
On-call veterans have debugged unfamiliar systems under pressure at 3am, and they understand viscerally why shortcuts are expensive. For backend, infrastructure, and platform roles, real on-call experience is a strong production-ownership signal. Courses and portfolios show other things well, and they do not show this.
Teams that own live services rotate on-call duty, typically in one-week shifts. The on-call developer carries an app that pages them when monitoring detects a problem, and severe issues expect a response within minutes. Compensation and how often the pager goes off vary widely between companies.