Redis pub / sub has worked fantastically for me - reached 100k+ concurrent users with ~80 msg / sec, but benchmarked much higher. It was the easiest, fastest, a

Redis pub / sub has worked fantastically for me - reached 100k+ concurrent users with ~80 msg / sec, but benchmarked much higher. It was the easiest, fastest, and most reliable solution I found (about ~4 years ago)