"In computer networking, cloud computing is computing that involves a large number of computers connected through a communication network such as the Internet, similar to utility computing. ...
Network-based services, which appear to be provided by real server hardware, and are in fact served up by virtual hardware, simulated by software running on one or more real machines are often called cloud computing. Such virtual servers do not physically exist and can therefore be moved around and scaled up or down on the fly without affecting the end user, somewhat like a cloud becoming larger or smaller without being a physical object. ...
Typically, the seller has actual energy-consuming servers which host products and services from a remote location, so end-users don't have to; they can simply log on to the network without installing anything. The major models of cloud computing service are known as software as a service, platform as a service, and infrastructure as a service. These cloud services may be offered in a public, private or hybrid network. Google, Amazon,leadsquared.com, Oracle Cloud, Salesforce, Zoho, Access2MyPC, and Microsoft Azure are some well-known cloud vendors." [Cloud computing. Wikipedia]
The AWS architecture diagram example "2-Tier Auto-scalable Web Application Architecture in 1 AZ" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the AWS Architecture Diagrams solution from the Computer and Networks area of ConceptDraw Solution Park.

This Azure cloud architecture pattern diagram template was created on the base of figure in the article "Valet Key Pattern" from the Microsoft Developer Network (MSDN) website.
"Valet Key Pattern.
Use a token or key that provides clients with restricted direct access to a specific resource or service in order to offload data transfer operations from the application code. This pattern is particularly useful in applications that use cloud-hosted storage systems or queues, and can minimize cost and maximize scalability and performance. ...
Client programs and web browsers often need to read and write files or data streams to and from an application’s storage. ...
Data stores have the capability to handle upload and download of data directly, without requiring the application to perform any processing to move this data, but this typically requires the client to have access to the security credentials for the store.
... applications must be able to securely control access to data in a granular way, but still reduce the load on the server by setting up this connection and then allowing the client to communicate directly with the data store to perform the required read or write operations. ...
To resolve the problem of controlling access to a data store where the store itself cannot manage authentication and authorization of clients, one typical solution is to restrict access to the data store’s public connection and provide the client with a key or token that the data store itself can validate.
This key or token is usually referred to as a valet key. It provides time-limited access to specific resources and allows only predefined operations such as reading and writing to storage or queues, or uploading and downloading in a web browser. Applications can create and issue valet keys to client devices and web browsers quickly and easily, allowing clients to perform the required operations without requiring the application to directly handle the data transfer. This removes the processing overhead, and the consequent impact on performance and scalability, from the application and the server." [msdn.microsoft.com/ ru-RU/ library/ dn568102.aspx]
The Azure cloud system architecture diagram template "Valet key pattern" for the ConceptDraw PRO diagramming and vector drawing software is included in the Azure Architecture solutin from the Computer and Networks area of ConceptDraw Solution Park.