I have benchmarked Crystal-Redis against several other client libraries in various programming languages in this blog article.
Here are some results:
Crystal: With this library I get > 680,000 commands per second using pipeline on a MacBook Air with a single client thread.
C: The equivalent program written in C with Hiredis gets me 340,000 commands per second.
Ruby: Ruby 2.2.1 with the redis-rb and Hiredis driver handles 150,000 commands per second.