 So, in this module students, we will talk about the Amazon Web Services Infrastructure. What is there on which the Amazon Web Services are working, they are running, so of course it is not possible to cover all of that tremendous infrastructure in a single module. But I will try to give you an overview of the Amazon Web Services Infrastructure and I will be covering two key main critical points, okay, what are those points making the hard choices about the hardware and examining the software infrastructure strategy of Amazon. Now these two points are critical and they encompass a lot about the infrastructure. Now one thing is very important to be understood is the commodity, okay, versus the branded. Now commodity servers are the machines which do not belong to a certain brand, they are not marketed in such a way, they don't have lots of bells and whistles, okay. Now of course, they don't have a higher price tag also. Now Amazon capitalizes on those commodity machines and these form the basis, the fundamental building blocks of Amazon Web Services. Of course, there are scenarios, there are cases when branded machines are also required and Amazon is known, the Amazon people are known to be cutthroat bargainers when it comes to branded machines. Number one, number two is that when we talk of branded machines, the underlying assumption is that the branded machines are run by enterprises, large organizations, and they are very reliable, okay. Now of course, reliability is important for Amazon Web Services also, but there is an associated cost also, branded machines usually typically most of the cases generally they cost more as compared to commodity hardware, okay. Now when we talk of branded machines, we say and we assume that they fail very infrequently or they are kind of fail safe, but when we talk of the Amazon environment, okay, which has hundreds and thousands, maybe a million servers, okay, then failure is an everyday thing. So at the scale of Amazon, branded machines can also fail. So why pay more, why pay a hand and a foot for branded machines when they are also going to fail, okay, as compared to the commodity hardware. Then of course, there is other equipment which is also used in such an environment such as batteries such as cooling fans, there are all of those things which are also there, it's not only hard disk, it's not only servers, that infrastructure has includes all of these things and on top of this, there may be scenarios, there may be instances, there may be requirements, when even there has to be custom designed hardware, custom designed hardware to support the Amazon Web Services infrastructure. Now come to the second point. Now the Amazon infrastructure is based upon virtualizations, okay, this is an abstraction. So we have these virtual machines which can be started, which can be stopped and which can be restarted, okay, so that is with the software and it is operated as a service. I am a user of Amazon Web Services, I am at a distance. I don't have hands-on local access, but still I am managing, still I am able to operate, still I am able to get the benefit of the Amazon Web Services without being at a close distance with no hands-on local intervention. That is the strength of the software infrastructure. It is designed for flexibility. Now the case of Amazon where the load is unpredictable, the load can go up, the load can come down unpredictably, so is the customers of Amazon Web Services, whose load can also go up and the load can also come down, okay. So this is, this application, this software infrastructure supports handling that kind of unpredictable load, load and unload environment, so to say. And then of course, this is highly resilient. It is highly resilient, it has to be fail safe and how it is made fail safe by making multiple copies of data, multiple copies of your bytes, okay, in say for example, in the S3 environment, all right. So when one instance fail, there is the second instance. The second instance, the E1, there is a backup for the second instance. And if the application starts with the first instance or only one set, then of course backup is added. Why? To add resilience, okay. So this is how the Amazon is able to offer the Amazon Web Services, okay, making hard choices about the hardware and coming up with a software infrastructure, which has all of these features built into it, okay. And these things are there in the Amazon Web Services public cloud and more details we will be discussing. Thank you. That's all for this module.