Ruby is integral to many modern web applications, and optimizing its performance can lead to significant gains. A study analyzing over 3,000 real-world Ruby services revealed that Ruby applications spend an average of 82% of their CPU time within libraries. This highlights the importance of selecting the right libraries for efficiency. Top contributors to CPU usage include stdlib (14.8%), activerecord (9.8%), and activesupport (8.1%). Although some libraries are irreplaceable, alternatives exist that can enhance performance, such as using pg for PostgreSQL over more CPU-intensive options like mysql2. Upgrading Ruby versions shows promise for performance improvement. Services running on Ruby 3 demonstrate lower CPU usage compared to those on Ruby 2, making migration worthwhile, especially with features like YJIT. Anticipation surrounds Ruby 4.0, which is expected to further enhance performance, particularly for workloads using the Set class now implemented as a core feature. However, not all upgrades yield lower CPU overhead; garbage collection remains a consistent CPU consumer across versions, accounting for 9.4% to 16.3% of total CPU usage. The article emphasizes the compute-intensive nature of Ruby applications and the critical role of library selection in performance optimization. It suggests that while many libraries are widely used, they aren’t always the most efficient options available. This insight encourages developers to reassess their library choices and consider version upgrades as part of their optimization strategy.