CAUTION : At this day (2017-10-12), Drupal commerce is very young. Therefor you can start the development of your e-commerce site but you may have bugs and security issues.
Example 1 (for drupal 7)
Step 1. Add file brows
Disable cache for a custom page from route declaration.
If you want to disable cache for a custom controller (Custom module), You have no_cache option (YOUR_MODULE.routing.yml).
File : mymodule.routing.yml
On drupal 8 every elements (almost) are an entity, as any entity you can render a node.
First, Create autocomplete controller and the route
Example of the controller : DefaultController.php
The metatag module provide an API (hook) to alter all meta tags : hook_metatag_metatags_view_alter
NOTE : This is not the drupal best practice.
This is a simple example of a web service. For the example, We will make a service to multiply two numbers.
Create JSON WebService module
Create a module.
Here : mywebservice
Download and Install
Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you.
Link : https://getcomposer.org/download/
Create a Drupal 8 module is a good idea, but develop as Drupal is BEST.
The famous tools PhpCS and PhpCBF allow you to check and correct (some) drupal coding standards and best practice errors.