Ask HN: What are some good back end website ideas?

I have to program a final project for my ap computer science class and I have programmed some websites before, front and backend, but I don't really have any ideas.

I have looked around online, but most often the suggestion is something boring like a twitter clone, instagram clone, etc.

Preferably it would be something that is more backend intensive, because that is what I will be graded on, but I am open to any suggestions. Thank you!