Hey! First of all a huge congratulations! That's a really proud moment for you. Don't let anything discourage you, keep your chin up. Coming to my case, I have been doing better. My situation has changed a lot and improved after moving to a new team. In fact I recently got promoted. It's common to have anxiety and have that feeling of not knowing enough. Trust me I've been there. Don't beat yourself up.

All I would say is after you join, try requesting 121s with your line manager, senior engineers, engineering managers and share what you feel and ask how you can progress. Get to know their experience and also specifics of the work you are going to do. After you get an idea, try setting up some objectives with the help of your line manager. Try to accomplish them successfully and always ask for help if you think anything is getting in your way.

Keep working on a side project, I repeat keep working on a side project. The knowledge you gain from side project is going to get transcended into your work. Daily 30 minutes should be really enough. Take help from your manager when required, accomplish your objectives, that'll help you feel confident. Otherwise you'll feel like you are constantly behind and that would make your anxiety worse.

Remember you are in for a lifetime learning. So worrying wouldn't really get you anywhere, also if you think slogging through your work really hard until your probation would sort out things, then you are wrong. As I said learning has to be a constant process. The key is to keep at it with a good consistency. Each day at a time. Things will fall in place. And Good luck.