Problem statement

Is there anyone to pickup the phone? Otherwise, we need to have a voicemail.

If the server cannot accept the request right away, we need to have a broker to store the message first.

RabbitMQ - AMQP 

ZMQ - TCP socket 

https://www.educba.com/zeromq-vs-rabbitmq/ 

Architecture of ZeroMQ

Components of RabbitMQ

Head to Head Comparison Between ZeroMQ vs RabbitMQ

Kafka