One of the biggest technical challenges I faced was during the release of the end-to-end bookmarking feature at Rakuten, which allowed users to bookmark items and view SKUs with live updates. The day after launch, a critical bug appeared that prevented users from bookmarking items. I was asked to fix it immediately without delaying production. I started by creating a minimal test case to reproduce the issue and discovered that the frontend relied on an API property that wasn’t consistent for certain SKUs. I quickly collaborated with a backend engineer to find a clean and reliable fix. During our discussion, I spotted there was a data field that was more stable but not yet exposed through the BFF layer. I proposed using this field instead, and after aligning with the backend engineer, I updated the backend logic to expose it. I then refactored the frontend code to consume this field and added robust fallback handling for safety. Next, I organized a cross-team regression testing session in the testing environment, working with engineers from multiple Scrum teams to verify there were no regressions. After stability was confirmed, I coordinated with the release team to deploy the hotfix the same day. The fix fully restored bookmarking functionality and led us to improve our data validation and release monitoring processes, helping prevent similar issues in the future.…One of the biggest technical challenges I faced was during the release of the end-to-end bookmarking feature at Rakuten, which allowed users to bookmark items and view SKUs with live updates. The day after launch, a critical bug appeared that prevented users from bookmarking items. I was asked to fix it immediately without delaying production. I started by creating a minimal test case to reproduce the issue and discovered that the frontend relied on an API property that wasn’t consistent for certain SKUs. I quickly collaborated with a backend engineer to find a clean and reliable fix. During our discussion, I spotted there was a data field that was more stable but not yet exposed through the BFF layer. I proposed using this field instead, and after aligning with the backend engineer, I updated the backend logic to expose it. I then refactored the frontend code to consume this field and added robust fallback handling for safety. Next, I organized a cross-team regression testing session in the testing environment, working with engineers from multiple Scrum teams to verify there were no regressions. After stability was confirmed, I coordinated with the release team to deploy the hotfix the same day. The fix fully restored bookmarking functionality and led us to improve our data validation and release monitoring processes, helping prevent similar issues in the future.WWWW…