[SavageBeast]

For an MVP I'd consider installing the database itself on the EC2 instance backed by EBS volume as opposed to going with RDS. Ive done it and I was surprised how well it performed for zero additional cost. Take care NOT to install anything on the SSD attached to the EC2 instance as it gets wiped on instance reboot (and thats not always up to you). Additionally, use IP whitelisting/security groups to restrict access to YOUR public IP for things like said database etc. Regarding public IP addresses, spring the fractional dollar and get yourself an elastic IP. I know the EC2 instance will have a public IP associated it but that can change where the elastic one is relatively permanent.

[ogarten]

For an MVP a SQLite database will probably be good enough, too. You make some good points!

Alternatively, go rent a virtual server for a couple bucks a months somewhere