The REST architectural constraints are primarily the design rules that clearly convey the distinct characteristics of the REST paradigm. These constraints aren't there to dictate what kind of technologies and tools to use; they just indicate how data gets transferred between the various components, such as clients and servers: 

• Separation of concerns between clients and servers: There is a clear disconnect between clients and servers. This unique separation enables the development and deployment of client-server applications independently. Any advancement and alteration of one thing doesn't affect the functioning of another. The decoupled nature guarantees the elimination of dependency-induced issues.
• Stateless communication: Server machines don't need to store any session information about the contexts of clients' calls. This means that any new requests can be handled by any server instance. However, the authentication details of clients in a session can be stocked so that new requests within the session don't need to be authenticated by the identification and access management system. 
• Clients to cache responses: Clients can cache server responses, since every server response comes with the decision enabling, cache-related details. 
• Connections may be direct or indirect: Clients can talk to servers directly or through intermediaries, which can be a proxy or other brokers. This separation increases system flexibility. The need for scalability is fulfilled easily with this intermediary.
• Uniform interface: The interactions between the various web application components (clients, servers, and intermediaries) get simplified due to the uniformity of their interfaces. If any of the components deviate from the established standards, there is a possibility that the web applications will break down. The four basic HTTP operations, GET, POST, PUT, and DELETE, provide the much-needed uniformity for all the contributing components to find, interact with, and accomplish tasks with clarity and confidence. The other operations, HEAD and OPTIONS, primarily deal with metadata management.
• Layered system: Layered and tiered systems mitigate development and operational complexities. Increasingly, there are many layers between the client and the server. These layers act as intermediaries, such as gateways and proxies, to automate some of the aspects of interactions. A proxy typically is an intermediary that's been selected by a client. The proxy provides interfaces to services, such as data translation, performance enhancement, and security protection. On the other hand, the gateway is another intermediary imposed by the network or server to provide an interface for specific services. 

Leveraging intermediary components leads to a substantial reduction in the interaction latency, security enforcement, and encapsulation of legacy systems. Thus, for the faster development of web applications and to make legacy applications more modern, modular, and web-enabled, the RESTful services paradigm contributes immensely. 

The simple object-access protocol (SOAP) mechanism is the original approach to access and use services. It's an XML-based messaging protocol that exchanges information among computers. There are a few perpetual issues with SOAP, and hence the origin and the dissemination of the REST paradigm, which is a comparatively lightweight and service-oriented application protocol, is widely appreciated. Due to the explosion in web applications and services, the creation and the sustenance of competent web architectures has become an important task.

The REST method is a famous architectural style that is closely aligned with the concepts used in the ubiquitous HTTP protocol. REST doesn't prescribe the details of component implementation and protocol syntax. However, it includes the fundamental constraints upon connectors, components, and data. This outlines the basis of the web architecture and, so the essence of its behavior as a network-based application. The REST paradigm illustrates a simple web application design and development through a set of architectural constraints. These architectural considerations ensure the scalability of component interactions, the standard interface, and the independent deployment of components. 

Precisely speaking, REST itself doesn't define where or how the state of various resources should be stored. REST specifies how the state can be retrieved using the ubiquitous GET operation. The state can also be provided through the PUT and POST operations. It's also possible to have read-only resources that just support the GET method. As discussed elsewhere, the resource state could be provided by any means, such as a filesystem, a dynamic combination of other resources, or physical sensors. The REST paradigm is an approach or design pattern for designing resource-oriented application services. That is, REST is an architectural style for networked applications. 

REST improves the performance, scalability, simplicity, and visibility of network-based applications. REST naturally encourages correct and efficient developer-computer and developer-developer communication. So, REST can be described as a way of building services and applications (we described a variety of software applications in the beginning of this chapter) by following a set of specific constraints between consumers and providers.