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The base software stack that runs on an EC2 instance is defined by your choice of Amazon Machine Image and any scripts or user data you add at launch time, and the hardware profile is the product of an instance type. A tenancy setting determines whether your instance will share a physical host with other instances.

As with all your AWS resources, it's important to give your EC2 instances easily identifiable tags that conform to a systemwide naming convention. There are limits to the number of resources you'll be allowed to launch within a single region and account wide. Should you hit your limit, you can always request access to additional resources.

If you plan to run an instance for a year or longer, you can save a significant amount of money compared to paying for on‐demand by purchasing a reserve instance. If your workload can withstand unexpected shutdowns, then a spot instance could also make sense.

There are four kinds of Elastic Block Store volumes: two high IOPS and low‐latency SSD types and two traditional hard drives. Your workload and budget will inform your choice. In addition, some EC2 instance types come with ephemeral instance store volumes that offer fast data access but whose data is lost when the instance is shut down.

All EC2 instances are given at least one private IP address, and should they require Internet access, they can also be given a nonpermanent public IP. If you require a permanent public IP, you can assign an elastic IP to the instance.

You secure access to your EC2 instances using software firewalls known as security groups and can open up secure and limited access through IAM roles, NAT instances or NAT gateways, and key pairs.

EC2 Auto Scaling can help you avoid application failures caused by overloaded instances. By implementing dynamic scaling policies, you can ensure that you always have enough instances to handle increased demand. In the event of some failure, a well‐designed Auto Scaling group will ensure that you always have a minimum number of healthy instances. When an instance becomes unhealthy, Auto Scaling will terminate and replace it.