there are three modes of usea reserved modewhereby you prepay to have cheaper per-hour accessa fixed per-hour rateand variable rate which depends on the overall compute market (when there is less demandthe costs are lowerwhen there is more demandthe prices go upfor testingyou can use single machine in the free tier this allows you to play around with the systemget used to the interfaceand so on howeverthis is very slow cpu machine thusdoing heavy computation using it is not advised on top of this general systemthere are several types of machines available with varying costsfrom single core to multicore system with lot of ramor even graphical processing units (gpuswe will later see that you can also get several of the cheaper machines and build yourself virtual cluster you can also choose to get linux or windows serverwith linux being slightly cheaper in this we will work our examples on linux but most of this information would be valid for windows machines as well the resources can be managed through web interface howeverit is also possible to do so programmatically and by setting up scripts which allocate virtual machinessetting up disksand all the operations that are possible through the web interface in factwhile the web interface changes very frequently (and some of the screenshots that we show in the book may be out-of-date by the time it goes to the press)the programmatic interface is more stable and the general architecture has remained stable since the service was introduced access to aws services is performed through traditional username/password systemalthough amazon calls the username an access key and the password secret key they probably do so to keep it separate from the username/password you use to access the web interface in factyou can create as many access/secret key pairs as you wish and give them different permissions this is helpful for larger team where senior user with access to the full web panel can create other keys for developers with less privileges amazon regions amazon com has several regions these correspond to physical regions of the worldwest coast east coast usseveral asian locationsa south american oneand european one if you will be transferring datait is best to keep it close to where you will be transferring to and from additionallyif you are handling user informationthere may be regulatory issues if you transfer it to another jurisdiction in that casedo check with an informed counsel on what the implications of transferring data about european customers to the us or vice versa are