There are loads of high quality advice here, so instead of repeating them I'll add one small bit I haven't noticed mentioned before. Publicly document the thin

There are loads of high quality advice here, so instead of repeating them I'll add one small bit I haven't noticed mentioned before. Publicly document the things that you 'discover'. Things you figure out or need others to tell you are in all likelihood going to be something any new junior developer coming in will need to 'discover' as well. Do this publicly, in the companies wiki for instance, as a way to show that you are learning. This will also be a way for you to bring actual value to the company and team. Finally, as has been mentioned we developers who are not new to this can still break things on production. I once broke NFC payments for all of the Android users that were using my employers banking application. While not an ideal situation, as long as you learn from these events then no one is going to throw you into the guillotine for them.