This document summarizes the key benefits of using the Elixir programming language compared to Ruby for building distributed, fault-tolerant, and highly concurrent applications. It notes that Elixir was developed to take advantage of modern multicore processors and borrowed concepts from Erlang like immutability, pattern matching, and functional programming. Several companies that saw success building large-scale systems with Elixir like Pinterest, Discord, and the NFL are highlighted. Elixir is recommended for projects that require high availability, scalability, or real-time features over Ruby which may require more servers and resources to achieve the same results.