A visitor opens a product page on your site and chooses a price. Paddle's checkout opens on top of the page. If the visitor is logged in, their email address is already filled in.

The visitor pays. Paddle shows them that the payment worked, and your site shows the Purchase Complete page.

Paddle sends your site a series of webhooks: the customer, the transaction as it is created and then completed, and for a recurring price the Paddle subscription. Your site saves each one in a queue and answers Paddle straight away.

The webhook processor, a Joomla scheduled task, works through the queue in order. It connects the Paddle customer to a Joomla account by email address, creating the account if there isn't one, records the transaction and creates an Access Subscription for each product bought.

If the Access Subscription starts now, the customer is added to the product's user groups and is sent a confirmation email. If it starts later (because it extends time they already have), it is scheduled, and they are told when it will start.

The lifecycle task, another scheduled task, starts Access Subscriptions whose time has come and ends those whose time is over, adding and removing groups as it goes.