What does damn this is hard mean in LLM era

I was playing with a offline-first mode with PowerSync to synchronize a local sqlite database with remote postgresql on server. "This might be a lot of effort," I thought. but then I paused. What would take a lot of effort? It's just a prompt with a couple of URLs to documentation. For a lot of changes I can just fire up claude code, tell it what to do and them merge without checking. But for something completely novel I froze. PowerSync has been out for some time and they have pretty extensive demos, but I still felt unsure, because it is something I am personally not confident in. For a REST-based website with blocks and a database, I am confident, and I am confident about LLM handling it properly. Once you add PWA and synchronization, I get rather cautious, because I am not sure I can do it, and I am not sure there are enough training examples. What if I completely destroy my app?

How do I know it does exactly what I want? How much testing do I need to do for this?

Damn, this is hard