For a sake of HA I'm considering switching from self hosted solution (ZeroMQ) to AWS Simple Notification Service for pub/sub in an application. Which is a backend for an app, thus should be reasonably real-time.
What are latency and throughput I can expect of SNS?
Is the app going to be hosted on EC2? If so, the latency will be far diminished, as the communication channel will be going across Amazon's connection, rather than through the internet.
If you are going to call AWS services from boxes not hosted on EC2, here's a cool site that attempts to give you an idea of the amount of latency between you and various AWS services and locations.
How are you measuring the HTTP Ping Request Latency?
We are making a HTTP GET request to AWS Service Endpoints (like EC2, SQS, SNS etc) for PING and measuring the observed latency for it across all regions.
As for thoughput, that is left up to you. You can use various strategies to increase throughput, like multi-treading, batching messages, etc.
Keep in mind that you will have to code for some side effects, like possibly seeing the same message twice (At Least Once Delivery), and not being able to rely on FIFO.