There are solutions for that: Shared NAS, sticky sessions etc.

Good luck with maintaining that NAS. Your sticky sessions will logout all users on a server that goes down. It's better to have a db.

Please stop.

Of course it's better to have a db doh... I'm replying to your

> By default flask doesnt have a db.

People don't have NAS laying around. And don't use a filesystem as a db, especially a remote filesystem.