microPython MQTT Callback implementation

[MMliam]

I've created a simple microPython client that publishes a message to a topic; the subscribing client acknowledges the receipt of the message. The acknowledgement is processed by the uPy client.

I'm curious as to how the Callback function in microPython functions; does is use interrupts, or is there a built-in loop in the publish method that waits for a callback (if set) after it sends the message?

[MMliam]

I've found the answer to my own question regarding callback implementation.

Thanks anyway, MM