Ποιοι τύποι web-API γνωρίζετε; Πώς διαφέρει ουσιαστικά το REST από το RPC;

Web APIs come in different types, the main ones are:

• REST (Representational State Transfer) — an architectural style that uses HTTP methods (GET, POST, PUT, DELETE) to work with resources identified by URIs. REST focuses on resources and their states.
• RPC (Remote Procedure Call) — calling remote procedures or functions, where the client invokes server methods as if they were local. Usually, method names and parameters are transmitted.
• GraphQL — a query language that allows the client to request exactly the data it needs.

Differences between REST and RPC:

• REST works with resources and their states, not with function calls.
• In REST, operations are standardized by HTTP methods, in RPC, specific methods with names are called.
• REST is more oriented towards data structure and presentation, RPC towards actions.

Example:

REST request to get a user:

GET /users/123

RPC request to get a user:

POST /rpc
{
  "method": "GetUser",
  "params": { "id": 123 }
}

Thus, REST is more declarative and resource-oriented, while RPC focuses on procedure calls.