We switched from Amazon's SQS to RabbitMQ, because SQS was killing our performance, and wasn't nearly as powerful overall. RabbitMQ gave us such a performance

We switched from Amazon's SQS to RabbitMQ, because SQS was killing our performance, and wasn't nearly as powerful overall. RabbitMQ gave us such a performance increase that we killed our database. We ended up having to rate limit RabbitMQ!