You might have a viva that’s finished in an hour or less, but it’s not very likely. You can hope, but that’s about all you can do.
Instead of hoping you get some rare occurrence, why not focus your energy on something that could help you more in your viva?
Read your thesis. Write summaries. Rehearse for the discussion. Do the work to be ready for what happens, rather than hoping you get a rare, short viva.