Phoenix LiveView vs Rails Hotwire: I Built the Same Real-Time App in Both. The Numbers Aren't Close

TL;DR — Phoenix LiveView delivers ~5× more HTTP throughput and establishes WebSocket connections ~14× faster under load. Rails is not broken — it's a mature, productive framework — but for real-time collaborative applications, the Erlang VM is a different league.

Why I Did This

Every time the Phoenix vs Rails debate comes up online, the arguments are the same: "Phoenix is fast but Elixir has a small ecosystem." "Rails is slow but you can hire Rails developers." Nobody shows numbers from a fair, controlled experiment.

So I built the exact same app twice — a collaborative real-time todo board — once in Phoenix LiveView and once in Rails 8 + Hotwire. Same features. Same HTML structure. Same Tailwind classes. Different everything underneath.…