What is the best model to make the use of Amazon AWS scale automatically?

Question

That is I have two models either by adding new instance or by upgrading type of instance. So, which is more preferable and in what circumstances which model should be used?

Answer 1

Your question is similar to the vertical vs. horizontal scalability concepts. It is a trade-off, and the best approach normally involves a mix of both, and mostly depends on the nature of your system.