What Is a Custom Live Pool in Microsoft Fabric Spark? — Explained

Pre-warmed Spark sessions. Libraries already installed. Network security policies respected. Sessions ready in 5–10 seconds. That is what a Custom Live Pool gives you in Microsoft Fabric — and it solves a problem the community has been asking about for over a year. In this short clipfrom my Fabric Insider Ep. 4 interview with Santhosh Kumar Ravindran — Principal PM for Spark Compute at Microsoft Fabric — we explain exactly what a Custom Live Pool is, how it is different from a Starter Pool and a Custom Pool, and when you should use it. Here is the problem it solves: ❌ Starter Pools — fast (5–10 second session start) but limited in customisation. You cannot add your own libraries or enforce network security policies. ❌ Custom Pools — fully configurable but require cold start time. Every session spins up from scratch — which means waiting. ✅ Custom Live Pools — the best of both. You get: 🚀 Pre-warmed sessions — 5–10 second start time, just like Starter Pools 📦 Libraries pre-installed — no waiting for library installation at session start 🔐 Full network security compliance — Managed VNET, workspace private links, CMK, block outbound access — all respected 📅 Scheduled hydration — schedule using an Outlook-style calendar: daily, weekly, or one-time This was the #1 enterprise ask for over a year from customers, partners, and MVPs. It is available on all F SKUs — including F2. 📺 Full Fabric Insider Ep. 4 interview with Santhosh Kumar Ravindran: https://www.youtube.com/watch?v=VayYW4REKzc 📝 Full blog post: https://radacad.com/fabric-spark-custom-live-pools-resource-profiles-performance-fixes-a-conversation-with-santhosh-kumar-ravindran-fabric-insider-ep-4/ 🎬 Full Fabric Insider Playlist: https://www.youtube.com/playlist?list=PLMXQvYI7QV6f8vUxtlFuGzQk-tYj3uOTn 🎧 Fabric Insider on Spotify: https://open.spotify.com/show/4eJrCr5UOWZ7ggmrVUce6l?si=Jx18sgdaScCgR3P1oDz-dw 💡 Power BI / Fabric Ideas: https://ideas.fabric.microsoft.com 💬 Microsoft Fabric Reddit: https://www.reddit.com/r/MicrosoftFabric/ 🌐 RADACAD: https://radacad.com 🔗 Microsoft Fabric Training: https://radacad.com/microsoft-fabric-training/ #MicrosoftFabric #FabricSpark #CustomLivePool #SparkPool #DataEngineering #FabricInsider #ApacheSpark #Notebook #FabricAnalytics #SparkPerformance #DataPlatform #FabricDataEngineering #SparkOptimization #BusinessIntelligence #FabricUpdates