Ask HN: A Sane Decision?

I am fatigued by evaluating databases for my project. There are so many disjoint features and options among these databases that it puts me in a dilemma on which DB to choose. As I am not a DBA, I was looking for a DB that will require bare minimum administration, is fault-tolerant, distributed, highly available, free and open source, does not force vendor lock-in, is performant and easy to use, is horizontally scalable, battle hardened and widely used. Looks like such database does not exist.

So I said to myself, heck with zero-downtime, distributed, fault-tolerant, highly available, horizontally scalable DB! I will go with vertical scalability instead and provision for backup; and do manual failover when such situation arises. Heck with zero-downtime.

I have decided to go with the following setup:

Three AWS EC2 instances. Two with AWS EBS, one for primary PostgreSQL node and the other for streaming replica of the primary node. The third AWS node will be for app server.

Is this a sane decision? What challenges do you foresee for me if I go with this bare minimum setup? Are there any improvements to this setup that you could suggest?