4 years in… how to fill in the gaps?

Well it's a great time to learn how to use AI tools because they are completely changing the day to day faster than anything else before! I have a background with top tier tech (Meta) and top tier interview prep (Formation) so this is my advice through that lens: 1. Everyone has gaps no matter what your background or experience. If you have INTERVIEWING GAPS (e.g. System Design and DS&A and struggle to perform) - those are one set of skills to work on. If you have gaps day to day and just feel behind - part is imposter syndrome and part is lack of work experience. Most people with CS degrees have a lot of internships and 4 years of CS that make you actually behind in work experience. 2. If you are trying to interview - which is sounds like you aren't, do DS&A like NeetCode, and SD like Hello Interview or other free and cheap options. 3. If you are just trying to level up on the job, honestly you want to put in more hours than anyone else at work and there isn't that much outside of work that will help more than just doing more work to **catch up on your experience gap.** You might be better off spending the leave LEARNING ABOUT YOUR OWN COMPANIES SYSTEMS IN DEPTH than learning about generic ones via 3rd party materials.