[Ruby 3×3 Goal Revisited: 6 Ways to Unlock Concurrency is a guide that organizes six core strategies for practically achieving concurrency and parallelism in the Ruby 3 era. It systematically covers criteria for choosing Ractors versus Threads, non-blocking I/O in web servers via Fiber schedulers, the impact of the GVL on native extensions and FFI calls, parallel map/reduce patterns for CPU‑boun..