So why go with AWS when there are options out there such as Microsoft Azure, where the underlying infrastructure is managed for you?
In my opinion, the biggest reasons are flexibility and control. PaaS services effectively 'lock' you into their platform. Applications designed for a particular PaaS vendor are not transparently transportable to other PaaS vendors. This can be a feature and a curse. By locking into a particular PaaS vendor, you are able to customize your application to take advantage of those features that are PaaS-specific (such as Azure). But by the same token, if you're not happy with your PaaS provider, you have nowhere to go, and the PaaS providers know it!
By keeping your application technology agnostic, you have the flexibility to 'shop around' if you need to.
What is the biggest benefit of all?
If you don't like the Cloud model, or for some reason security changes within your company, you can bring your entire application back in-house at any time with minimal changes.
Note
IaaS providers such as Amazon AWS give you the opportunity to rollback your migration to the cloud at any stage and allow portability between providers.
AWS has been around for a while now, and was one of the first IaaS providers of any size in this space. But does that mean they are the best?
Well in my opinion, yes. While they are not perfect by any means, they have one thing which other IaaS vendors cannot match, and that is scale. The size of the compute capacity that Amazon provides is in the order of magnitude greater to their closest rival, which means the chances of you not getting capacity from the pool when you need it is that much less. AWS is also innovating, in my opinion, faster than their closest rivals; this means that if you are using AWS, those innovations become available as soon as they are released.
But AWS is not infallible.
Because AWS is the biggest, it is also the greatest in demand. This means that on occasion (rarely though) you may be denied new service requests within a particular availability region. Luckily though, your existing services will always run ok.
This means that you will still need to manage the growth of your cloud application in advance. If you think that because your application is in the cloud it is 'infinitely' scalable, then think again! Amazon—just like any other provider—still has to manage spare capacity at any given time. Too much, and Amazon is paying for capacity that will never be used, and too little, and they will run out just when you need it.
However, it is public knowledge that Amazon does not use AWS for their own bookstore. These resources are managed outside of the AWS envelope. So peak periods on the Amazon bookstore will never impact your AWS cloud applications. However, in general, Christmas will! So beware of peak periods, and manage your capacity in advance, just in case.
Tip
Also beware of instances which may shut down or IP addresses which change unexpectedly; AWS does not guarantee that your instance will always be available or that your IP address will always remain the same. You will need to design for these eventualities (something we will address as we progress through the chapters).
So what's driving you to read this book?
Well we suspect that you have heard and read a lot about the 'cloud', and you are interested in finding out how the cloud can benefit your organization. Certainly, you don't want to be left behind, and certainly the thought of getting your hands on as many servers as and when you need them is an attractive proposition.
You may be thinking of using the cloud only for development and test at this point, which is perfectly ok. This is much like how virtualization was initially used, and look how quickly that moved onto production systems.
You may have a brand new application ready for development and you find the thought of lock-in to Azure too restrictive.
But no matter what your driver is, it is now time for your enterprise to embrace cloud computing.