Comment Depends on what you mean by serious I suppose (Score 1) 80
Is an ETL system that ships literally 10's of millions of records an hour (doesn't even break a sweat, could be doing 100's of millions or even billions), or a reporting system that serves tens of thousands of reports a day, shipping them direct from the database to S3 at around 40MB/s (it could go faster, the application isn't the limiting factor in this case), all running 24/7 with basically no maintenance required serious? To be fair, it runs on jRuby, not MRI Ruby, so I'm leveraging native JVM threads and Java libraries all over the place in these two different codebases, but the bulk of the actual code is still just Ruby.