[worewood]

99. ..% of "real" applications are bottlenecked by I/O, be it disk or network or synchronization (as in, waiting for something else to happen)

If you're not in a HPC or heavily resource constrained context you can safely ignore the performance implications of choosing whatever programming language you like.

[azylman]

This isn't really true, some languages handle I/O much better than other languages. We migrated a Python application to Go that was about as simple as you can get and mostly blocked by I/O (call DB, transform storage format to Thrift, respond to caller with Thrift) and saw SUBSTANTIAL improvements in performance. Approximately 40% improvement in p99 latency and, more notably, 15x improvement in throughput.