I wouldn’t personally see the use of AMQP 0.9.1 as a warning sign, as RabbitMQ is a very stable and mature AMQP implementation (the best one if you ask me) that I’ve been using in real production workloads for more than a decade now. It never failed me and was able to handle massive message traffic over the years. Moreover, the community is working right now in implementing AMQP 1.0 (see https://github.com/rabbitmq/rabbitmq-server/pull/9022).