Tell me about a time when you had to deal with a critical project, and why was it critical

One time I worked on a checkout issue where some customers couldn't complete purchases after a backend change. It was critical because it was customer-facing and directly affecting revenue, even though my part was only one service in the flow. I was responsible for tracing the failure in our service, and once I found that a validation change was rejecting valid requests, I raised it right away instead of waiting until I had everything solved. I paired briefly with a senior engineer to confirm the safest fix, then I implemented it, added a test for that case, and stayed involved through deployment. We restored the checkout path that afternoon, and afterward I documented the issue so we could avoid the same regression in future releases.

At my previous job I was the junior front-end developer on an educational app, and QA flagged that students who use screen readers couldn't complete the course sign‑up flow. It was critical because we were about to roll the product out to partner schools and excluding those students would have broken our accessibility commitments and harmed real learners. I reproduced the problem using a screen reader, traced it to missing labels and a confusing focus order, and then updated the markup and keyboard handling to restore a logical flow. I worked with the UX designer to confirm the interaction felt right, added an automated accessibility check to our CI so it wouldn't regress, and stayed through the deployment to validate the fix in production. Afterward I wrote a short accessibility checklist for the team so future pages would be built with those basics in mind.