It should be noted that the issue of security is not the topic of this book. We will not discuss how to secure the systems overall, but we will touch lightly on some concerns and how it is possible to use Amazon-provided services or configurations to start the movement into that world.

With that said we will use the following example: suppose the instances we wish to bring up do not have internet access but still need to talk to other instances. This could be for security—as it prevents outside access to our instances and adds a layer of hardening—or for simplicity. This is very relevant in the microservices architecture if it can be architected in such a way that outside connectivity is not needed.

To do this, we can use a Network Address Translation (NAT) instance in our environment to our advantage. We can set up our normal instances to send their non-local traffic to this NAT instance. By doing this, we can effectively turn on and off access to the outside internet...