Broadcast grade color scopes, inside a LiveView

A few months ago we needed real video scopes inside our Phoenix app. Not toy histograms. The actual four you see in DaVinci Resolve, Baselight, Nuke: waveform, RGB parade, vectorscope, histogram. Colorists grade with these. If yours are off, people stop trusting the tool within about ten seconds.

I looked at the ticket and thought, “ok, this is where we finally bolt on a separate frontend”. Turns out no. A LiveView hook and about 900 lines of WebGL later, the scopes were running at 30 fps next to the grading controls, and the Elixir side was basically asleep.

At CyanView, we run a Phoenix LiveView application on embedded hardware. Out of the box, the BEAM VM was eating 300MB of RAM at idle and keeping the CPU at 45%. After tuning, we got it down to ~120MB and 5-10% idle CPU.

Here’s exactly what we changed and why each thing matters.

Due to an NDA we can’t go into specific business details, but here’s the gist: we inherited a SaaS platform in the accounting and document processing space. The system handled document ingestion, automated data extraction, workflow orchestration, and multi-tenant reporting a fairly typical B2B back-office tool. The original stack was maintained by a team of two backend engineers and one frontend developer. What follows is a breakdown of what the migration to Elixir/Phoenix looked like by the numbers.

If you’re running a Phoenix LiveView application and your iOS Safari users are experiencing frozen pages, slow reconnects, or 10+ second hangs after returning from sleep this article is for you.

I’ve been running a production Phoenix LiveView application. The app worked great on desktop, but iPhone users kept reporting the same thing: the page would freeze or hang for several seconds after switching back from another app or unlocking their phone. Sometimes the page would never recover at all.

The Phoenix LiveView Reconnection Bug: A Deep Dive

I encountered a critical bug in a Phoenix LiveView settings page that controlled hardware via MQTT. When the WebSocket connection dropped and LiveView automatically reconnected, stale form values were being sent back to the hardware, overwriting the current hardware state.