It is easy to integrate with the solution and uncomplicated to add new things later. It is also easy to move onto something else, if you change your mind.

Do not duplicate data if you don’t have to! If you can, use the POS as master and let the POS calculate prices and carry the basket.

Most modern POS solutions of today have readymade APIs for this type of integrations. Sometimes they are called Omni channel or eCommerce APIs.

If the POS is old, without any good APIs, build a small plugin or middleware to make the EasyShop API fit the legacy solution.