Let's make ruby the best language in the world by giving it the speed of C. Ruby's goal is maximize programmer happiness, not the happiness of computers. But sometimes we still need to give some sympathy to the poor machine, especially when our API requests timed out. There're multiple ways to speed up Ruby by running C under the hood. Among them, FFI (foreign function interface) is the one that give us the most pleasant experience. With FFI, we can use C libraries without writing a single line of C code. Better yet, we also get cross platform/implementation support for free. We'll start from how FFI works, then calling a simple c function from ruby. Explore more by bridging C structs to ruby class and handing C pointers. Conclude with a FFI example.