就 usually means "faster than I expected".You can also use 你这就到了？ same meaning. e.g. A and B have a date in a cafe in 3PM.B sent A a message on 2:40 PM saying that he/she already in the cafe. A reply 你就到了？

I think it is not a question. so don't use question mark. I explain it "then" . That should not only a single sentence. That must have other context 你就到了= then here you are.

Leroy the full sentence is the title.

Here 就 means /right away/at once/as soon as/ In this sentence, it means "just".

This word is one of the common conjunction words, there is no meaning saying it alone, so could you let me know the full sentence you are saying?