Seems like it could be better to store the state in a database and create a unique, short ID that goes in the URL, especially if your doing server rendering (like SSR react or HTMX, or rails/Django)
> I also didn't want to store anything on the backend (at least for the free tier).
You can make the state unique in the DB by a user cookie ID and then upsert the state which will overwrite older state with the latest state. Then you only have 1 record per free user. Remove record that haven’t been modified in 30 days and you don’t have much overhead. Just off the cuff thinking.