Though explaining cloud computing is not in the scope of this book, I will explain it in just one paragraph. Any business, big or small, needs hardware infrastructure and different software installed on it. An operating system is the basic software needed, along with different servers (from a software perspective) for storage, mail, Web, database, DNS, and so on. The list of software frameworks/platforms needed might end up being large. The point of interest here is that the initial budget for this hardware and software platform is high; we are not even considering the real estate needed to host it. This is where cloud computing providers such as Amazon, Rackspace, Google, and Microsoft come into play. They have hosted high-end hardware and software in different data centers across the globe and let us choose from different configurations to start an instance. Then, this is accessed remotely over the public network for management purposes. Literally, all our setup is done in the cloud provider's data center, and we just pay as we use. Shut down the instance and you stop paying for it. Not only small start-ups but large enterprises also often temporarily fall back to cloud servers for a temporary rise in the computing resource demand. The prices offered by the providers are very competitive too; particularly, Amazon Web Service (AWS) of all of them in my opinion and its popularity says it all.

The wiki page at http://en.wikipedia.org/wiki/Cloud_computing has a lot of detail, perhaps a bit too much for someone new to the concept, but it is a good read, nevertheless. The article at http://computer.howstuffworks.com/cloud-computing/cloud-computing.htm is pretty good and I recommended that you read it if you are not aware of the concept of cloud computing.

In this chapter, we will set up MongoDB instances on the cloud using MongoDB service providers and then, by ourselves on AWS.