The scaling story in Elixir is so nice, I just implemented eventual consistency for calculating average ratings on a Class/Instructor level and it was 20 lines of code in a GenServer that can be tested and is super clear how it works. I'm not even sure how you'd do something like this in Javascript or Python but it would probably involve extra infrastructure that is another moving piece to deploy, manage and can be a cause of potential failures. The same is true with rate limiting and something like Hammer (https://github.com/ExHammer/hammer).