Describe a time when you disagreed with your manager or team. How did you handle it?

Situation: My manager wanted to implement a custom authentication system for our new product instead of using an established OAuth provider. He believed it would give us more flexibility for future features. Task: I disagreed because I had seen custom auth systems become major security liabilities at two previous companies. I needed to advocate for a different approach without undermining my manager's authority. Action: Instead of pushing back in a team meeting, I scheduled a 1-on-1 with my manager. I prepared a comparison document showing: the development time for custom auth (estimated 4-6 weeks) vs. integration time for OAuth (1 week); three CVE examples from companies that built custom auth; and a cost analysis of potential security audit requirements. I acknowledged his point about flexibility and proposed a compromise: use OAuth for authentication but build a custom authorization layer for the specific flexibility he wanted. Result: My manager agreed to the compromise. We shipped auth in 8 days instead of the projected 6 weeks, and the authorization layer gave us the flexibility he originally wanted. During a security audit six months later, the auditor specifically noted our auth approach as a strength. My manager later told me he appreciated that I brought data rather than just opinions.