Tell me about a situation that required you to dig deep to get to the root cause.

In my first year, I worked on a bug where some users were getting duplicate confirmation emails after signing up. At first I thought the email service was sending duplicates, but when I compared successful and failed sign-ups, I noticed it only happened when the first request timed out and the client retried. I reproduced that flow locally and found our endpoint created the account before returning an error, so the retry triggered the email again. I fixed the flow to make the operation safe to retry and added a test for that exact case. After the next release, we watched the logs for a week and the duplicate emails stopped.

At my second job I noticed several support tickets from new users in Latin America who couldn’t upload profile photos — the client showed success but the server never received the file. I cared a lot about making the product work for everyone, so I reproduced the issue with filenames containing accents and inspected the request traffic and server logs. I discovered our middleware was silently dropping non-ASCII filenames when normalizing paths before storing them, which only happened behind our production proxy. I fixed the normalization to safely handle UTF-8, added a server-side fallback to rewrite problematic names, and added an automated test that uploads files with a variety of characters. After deployment I followed up with those users and the support queue cleared, which felt good because the fix addressed an accessibility and inclusion problem, not just a crash.