Describe a time when you mentored or onboarded a junior engineer. What structure or resources did you provide, how did you assess their progress, and how did you adapt your approach when challenges arose?

When our team hired a junior engineer onto our eight-person backend team, I owned their 30-60-90 onboarding. I created a 20-item runbook (architecture overview, CI steps, five starter tickets), scheduled three pairing sessions per week, and gave them two small ownership areas to iterate on. I assessed progress with weekly one-on-ones, PR metrics (comments per PR dropped from 8 to 3) and time-to-merge (from 4 days to 1.5 days), plus defect rate in their modules (down 40%). When they stumbled on async patterns and flaky tests, I swapped lengthy docs for focused 1:1 whiteboard walkthroughs and 90-minute mob sessions. That shift cut their ramp to full ownership from the planned six weeks to four, and they closed six tickets across the next two sprints.