What is REST API / Representation State Transfer

Restful Web Server/Application? Web application that implements HTTP CRUD methods in Restful way. Eg: Twitter, facebook are implemented using restful APIs.
When web-client calls Restful APIs then Web-Server can return JSON or HTML or XML

How REST Works?


1. Web server(abc.com) defines Resources(Eg: Customers, movies, cars etc) and exposes a service/End point 
eg:(https://abc.com/api/movies), where
abc.com  : Domain
api      : Convention(mostly used by companies) to expose RESTful services
movies   : Resource
2. Web client will use above END POINT(https://abc.com/api/movies) to talk to Web service to perform CRUD Operations on Resource
3. Perform CRUD Operations on Resource.

          Web Client                                         Web Service
GET www.abc.com/api/movies HTTP/1.1       --------->           Query list of movies
                        <-[ {id:1,'movie1'}, {id:2,'movie2'} ]-

GET www.abc.com/api/movies/1 HTTP/1.1    --------->         return id=1 movie
                              <-[ {id:1,'movie1'} ]-

POST www.abc.com/api/movies {id:3, 'movie3'} HTTP/1.1  --------->  Add object [ {id:1,'movie1'}, {id:2,'movie2'}, {id:3,'movie3'} ]
PUT www.abc.com/api/movies/1 {id:1, 'movie11'} HTTP/1.1 ---------> Updates db [ {id:1,'movie11'}, {id:2,'movie2'}, {id:3,'movie3'} ]
DELETE www.abc.com/api/movies/1 HTTP/1.1             ---------> Delete object [ {id:2,'movie2'}, {id:3,'movie3'} ]


Client	                        	                Web Service
http:///api/resource-name
                                        Implement APIs GET(){..} POST(){..} PUT(){..} DELETE(){..}
                                <---data----

Why RESTful?

1. Rest makes Web Service OS Independent: Web applications can reside on different operating systems, some could be on Windows, and others could be on Linux.
2. Rest makes Web Service language independent: Web services can be implemented in any language(C++,RUST etc)
3. On Cloud: RESTful applications are moved can reside on cloud. Azure and Amazon provide a lot of API’s based on the Restful architecture.

Comparison

REST vs HTTP

REST HTTP
What Set of rules L7 Protocol
Focus Resource Methods to get

REST vs SOAP(Simple Object Access Protocol)

REST SOAP
Why To access web service same
Flexible more Less, hard to use
Relies on JSON,XML,CSV,RSS XML, CORBA(Common Object Request Broker Architecture) rely on binary messaging

REST vs gRPC

REST gRPC
What Method to implement API same
size,speed less(uses json) Better. Uses Protocol Buffers (protobuf) as its interface definition language.
This binary serialization format is more efficient in terms of size and speed
Communication 1 direction Bidirectional. both the client and server to send a stream of messages
Efficiency HTTP/1.1 More. uses HTTP/2 for transport

Versioning

What? Version numbers (like v1, v2, etc.) added to REST APIs

Why? Allows developers to introduce new features, deprecate old ones, and make modifications without disrupting existing applications
Eg: new authentication methods, performance optimizations, security methods might be added to v2

How versioning is implemented

URL Path Versioning (Most Common, easy to identify)
version number is embedded in the URL path, such as /api/v1/resource

GET /api/v1/users
GET /api/v2/users
Header-Based Versioning (less visible)
version information is provided in the request headers

GET /api/users
Header: API-Version: v1
Query Parameter Versioning

GET /api/users?version=1
Accept Header Versioning (Media Type)
Sometimes, the Accept header is used to specify the version

application/vnd.example.v1+json

Code Implementations

Python flask-restful

Rust Actix_web Http Server exposing REST APIs