PHP
Use the latest version
Use the PHP-FPM handler
Use opcache
- note : you must restart php after updating your project code so It might have a downtime of the backend for few seconds.
Use app caching ?
- A DB request is always the same in frontend, ie. no filters, search ...
- CPU heavy load : image resize, tables joins / databases
Queues
Queue are the best way to defer an operation in a non blocking way for the user.
Use queues when something take more time than a db request :
- call to an api
- call to an external service (linux base)