Ideas for a poor man's robust/efficient server setup

[Olivier Henley <olivier.henley@gmail.com>]

Hi all,

Because I know some of you as seen and built really robust stuff, I would appreciate any advice on how to achieve a sound/good enough robust server on the cheap side.

What  it is:
-	Web app, real-time user generated content; will get highly dynamic as more people interact. Potential for high traffic; millions.
-	Using Gnoga and MySQL ... for now.
-	Using Nginx to failover between web app exec in case one crashes. Same machine.
-	One man show project ... for now.
-	Would spend max 50$ CAD per month to host ... for now.
-	I have no problem limiting the number of concurrent connections to stay on the safe side and take the time to upgrade my setup. 
-	I already have a  dedicated box: 8 C / 8T @2,4 Ghz x64, 16 Gig, 250Gig SSD, 99.9% SLA (16$ EUR ~ 25$ CAD)
-	Minimum Viable Product completed. Moving on small scale test phase.

What I want:
-	Proper setup to move on, without too much damage, to other infra; to scale. 
-	Near zero downtime.
-	Robustness for my service. (db, connection etc)
-	Snappy service. Respond/React quickly.

I need guidance/advice/ideas on the following:
-	Should I move away from MySQL? What are my options using Ada and Gnoga? NoSQL, persistent objects? 
-	Fast failover configuration options; DNS level or the sort.
-	A general setup/recipe for a poor man's 'robust' setup? 

Right now I am exploring those ideas:
-	DB at AWS RDS MySQL in configuration Multi-AZ. (scale, managed, redundant, robust)... but I can only pay for poor perf and little space
-	Using AWS highway 53, 2 small EC2 instances (in case one fails) that redirect to 2 dedicated servers (in case one fails) available on 2 different regions. (eg: one montreal, one paris). I feel this setup is overthought though.

 
A big thank you in advance,

Olivier

p.s: I know I might be dreaming a bit but I try to prepare the best I can and do my best with what I have.