Ask HN: What to learn as a back end developer

My employer is offering us to do some java certification or other learnings during the work hours. I will definitely take up this offer but I was thinking is getting java certificate even worth it? The employer is not demanding that I do java learnings I can chose some other stuff aswell if I want to.

I am turning to you guys to recommend me anything intersetng that could be useful for my career and my employer

I am interested in devops, backend engineering, blockchain, opensource etc...