This article discusses how Ruby applications often consume a lot of CPU time, primarily due to library choices. It highlights key libraries impacting performance, the benefits of upgrading to Ruby 3, and the expected improvements with Ruby 4.0.

Ruby's JIT compiler, specifically ZJIT, enhances performance by compiling frequently used methods into native code while retaining their bytecode for safety and de-optimization. The article explains the mechanics of how Ruby executes JIT-compiled code, the criteria for compilation, and the reasons for falling back to the interpreter when assumptions are violated. Additionally, it addresses common questions regarding JIT functionality and performance implications.