I TIL - firecracker, thank you for that! :)
Great article and project, i didn't understand the idea of using RabbitMQ and fetching for new events in a loop. I am not an architect, but i was thinking that real-time databases, are used for those purposes?
About the containers - if you are not running them in privileged mode, you should be pretty secured, especially by limiting what kind of binaries the containers have.