This extension works by listening to a number of Magento events via the Observer classes in /Observer. The observers then publish events to the kustomer_event table defined in /Setup/InstallSchema.php.
Once every minute a cron job runs the send method in /Model/Event.php which is responsible for checking events in the database that have not been sent and attempting to send them to Kustomer. If the request succeeds the is_sent column is marked to a 1 and the event will be excluded from future sends. If the request fails we will iterate send_count until we hit a max number of attempts. Requests are sent to the magento-api service in Kustomer.
Once a day we will also run a clean method in /Model/Event.php which will delete any events that have already been sent or have hit the max number of attempts. This will keep the database table from growing overly large.