title: several t2.micro better than a single t2.small or t2.medium
body: <p>I read EC2's docs: <a href="http://aws.amazon.com/ec2/instance-types/">instance types</a>, <a href="http://aws.amazon.com/ec2/pricing/">pricing</a>, <a href="http://aws.amazon.com/ec2/faqs/">FAQ</a>, <a href="http://aws.amazon.com/ec2/instance-types/#burst">burstable performance</a> and also <a href="http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/t2-instances.html#t2-instances-cpu-credits">this</a> about CPU credits.
  I even asked the following AWS support and the answer wasn't clear.</p>
  
  <p>The thing is, according to the docs (although not too clear) and AWS support, all 3 instance types have the same performance while bursting, it's 100% usage of a certain type of CPU core.</p>
  
  <p>So this is my thought process. Assuming t2.micro's RAM is enough and that the software can scale horizontally. Having 2 t2.micro has the same cost as 1 t2.small, assuming the load distributed equally between them (probably via AWS LB) they will use the same amount of total CPU and consume the same amount of CPU credits. If they were to fall back to baseline performance, it would be the same.</p>
  
  <p>BUT, while they are bursting, 2 t2.micro can achieve x2 the performance of a t2.small (again, for the same cost). Same concept applies to t2.medium. Also using smaller instances allows for tigther auto (or manual) scaling which allows one to save money.</p>
  
  <p>So my question is, given RAM and horizontal scale is not a problem, why would one use other than t2.micro.</p>
  
  <p>EDIT: After some replies, here are a few notes about them:</p>
  
  <ul>
  <li>I asked on AWS support and supposedly, each vCPU of the t2.medium can achieve 50% of "the full core". This means the same thing I said applies to t2.medium (if what they said was correct).</li>
  <li>T2.micro instances CAN be used on production. Depending on the technology and implementation, a single instance can handle over 400 RPS. I do, and so does <a href="http://hipsterdevblog.com/blog/2014/12/19/how-far-can-you-go-with-haproxy-and-a-t2-dot-micro/">this guy</a>.</li>
  <li>They do require a closer look to make sure credits don't go low, but I don't accept that as a reason not to use them.</li>
  </ul>