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REST API: The Concept

REST stands for "Representational State Transfer". This is an architectural style. A web API conforming to this style is a REST API.

REST stands on 6 guiding principles, important among them are:

  • Client-server: separate backend and frontend.
  • Stateless: each http request contains enough data (e.g. auth, session, user data) to understand it without knowing what the previous request was.
  • Cacheable
    • GET: always
    • POST: using http headers expire, cache-control, etag, last-modified
    • PUT, DELETE: never


The following are some important, concise, and simplified REST concepts a good backend dev must be familiarized with.


REST APIs are modeled as a resource hierarchy - where each node is either a collection, or a single resource. A single resource has some state, or sub-resources.

Example of a stateful resource is the following, where a user resource has data/states:

POST /users/:id

  id: 4e7d418a70f,
  name: 'muhammad',
  country: 'earth',
  verified: true
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Example of a resource with sub-resources is the following, where a user has multiple projects, each of which are a resource.

GET /users/:id/projects
content-type: application/json

    id: 'postman cli',
    desc: 'postman implemented in command-line'
    url: ''
    id: 'typescript',
    desc: 'typescript is a superset of javascript',
    url: ''
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API Idempotency means "a client can make a request multiple times, returning same response - without having any side-effect".

Making the following requests multiple times produces the same result, and has no further side-effect - thus are "idempotent" APIs:

  • GET /users/:id - just retrieving same user data
  • PUT /users - just updating same json data
  • DELETE /users/:id - just deleteing the same user

A non-idempotent API:

  • POST /users/:id - because a new user will be created everytime this request is made

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