[ra]

If those are the tools you are familiar with, then go for it.

Stick with a SQL database and ORM for now, you can always convert to NoSQL later if you need to.

Most would suggest using one of the leading two modern framework combos for greater productivity (Django or Rails).

If you already know a few languages then you should pick up Ruby or Python pretty quickly.

Personally, I use Django - but in a previous life I did a lot with Spring + Hibernate; and whilst Java isn't trendy for startups, it is a potent combo.