Don't Block the Event Loop: Scaling Heavy Video Rendering with Node.js, Redis & BullMQ

When I first started building Foog Animation Studio (part of our SaaS ecosystem at Foog Technology ), I hit a massive wall: Video rendering is computationally expensive. If you try to process a 1080p video with transitions using FFmpeg directly inside your main Express controller, your Node.js Event Loop will immediately block. Your server will stop responding to other users, APIs will timeout, and your app will effectively crash under pressure. Here is how we solved this architectural nightmare and built a system that scales seamlessly. ❌ The Naive Approach (What NOT to do) As developers, our first instinct is often to just exec a child process and wait for it. // 🚨 Anti-Pattern: Blocking the main thread visually (even if async, it eats resources) app . post ( ' /api/render ' , async ( req , res ) => { const { images , text } = req . body ; // Running heavy FFmpeg tasks right in the API layer await utils . renderVideoLocally ( images , text ); res . json ({ status : " done " , videoUr