A scalable cloud web application is one if it is able to grow or shrink in terms of compute power and storage, as and when a situation demands. The factors which create such a situation are: An application which has low or moderate usage most of the time and experiences sudden increase in usage during certain times.
Example: Let's say you run an online Pizza Shop, and demand is consistent during the working days of the week and there is surge in demand during weekends. In such a scenario, you should be able to instruct Azure to scale the application resources to be able to handle this surge.
Consider another scenario in which you have done some promotional work and anticipating a surge in demand you can instruct Azure to handle this surge for a week or two.
These scenarios clearly show that great flexibility is required in increasing and decreasing compute power to run and maintain a large web application.
To restate a scalable cloud application is one which can scale up and scale down as per demands. You may have a question at this moment 'Is developing a scalable application different from developing a non scalable application'. Yes, it is different. You will know the difference when we answer the question on Web roles, workers roles and cloud services.
Problem with local data center or with web host :
If we were to handle this situation in our local datacenter we would have to opt for additional hardware to meet the requirements during sudden spikes in traffic. If the application is running on a web host, you would have to take the traffic spikes into account and subscribe for the appropriate plan. Over a period time, you may end up paying more for resources which the web application may not utilize fully.
Traffic spike refers to a sudden appreciable increase in web traffic to a web site or a web application.
A web host is a company which offer services to locate your web applications on their servers and display them on requests by end users. A web host ahs to
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