Actually, it's both! Messenger is one of the newest parts of Symfony and we absolutely ❤️ it. In this tutorial, we'll create an important application that asynchronously adds our favorite cat (Ponka) to all of your favorite photos. Along the way, we'll learn to:

Create a messages classes
Add & configure "handler" classes that do the work
Dispatch messages through the bus
Configure "transports" for async messages
Route messages to transports
Execute "worker" processes that "consume" queued messages
Things fail!? Retry message and set up the "failure transport"
Middleware
Add & understand message stamps
Prioritized transports
A little CQRS: a Query bus
Testing & Dev: handling messages "sync"
Deployment and supervisor
RabbitMQ & AMQP

https://symfonycasts.com/screencast/messenger