Here's an example question and answer for a competency based behavioral interview question using the STAR framework.
Situation: When I worked as a product manager at Rent the Runway, I noticed that the marketing team often struggled to keep promo codes consistent across devices, through our home-grown CMS.
Task: They wanted to be very specific with targeting users, and all of our front-end platforms handled the logic separately.
Action: I proposed and lead the project to move the logic of deciding what to display to the backend, rather than the frontend. I worked with a backend engineer, a front-end engineer and an iOS developer to revamp our promo code endpoint to return one single, source of truth result, based on the user ID that got sent with the request. On the backend, we implemented a robust CMS parser that allowed the marketing team to mix and match most possible user attributes through the CMS and check them against the user ID that was sent. Now someone who's birthday was coming up, who had a PRO subscription and hasn't ordered in at least a month would get a very different promo code than someone who just signed up.
Result: The project ultimately had three great benefits. First, it allowed for much more nimble marketing campaigns that could run independently from app releases. Next, it relieved us from the burden of constantly making sure we're backwards compatible at each CMS update. But most importantly, it kickstarted the process of transitioning to a backend-driven UI across the company, which I understand is something that's on your roadmap as well.
This is a solid answer that reveals enough detail to avoid being too generic, and at the same time doesn't overwhelm the interviewer with redundant information. The bulk of the answer is in the Action bit. The Result bit explains several benefits to the previous company and how that can be useful for the current one.
If you have any questions, comments or concerns, open a Github Issue on this repository.