Hi, how are you?
I have a question? how much message/sec you think can require?
more than a or two millions?
I can provider to you a queue server with apache kafka, he is really good choice by performance, is the better queue server open source.
If you like i can provide to you an more easy way to implement push notifications on real time with this technologies, you don't need to pay by lambda messages.
Additionally you can upgrade apache kafka and implement on a cluster.
Any way if you like your chooses technologies, i can provide this to you, is same architecture with different technologies.
Thanks, bye.
-Carlos Cañón.