--- title: "Why do I need Unikraft? I'll just grab Firecracker" description: "Firecracker is a superb virtual machine monitor, but it is only one component of a full platform. Here is exactly what you get when you run Unikraft instead of building it yourself." doc_version: "1.0" last_updated: "2026-07-14" --- Firecracker is superb! In fact, we run a hardened fork of it in production. But Firecracker is a virtual machine monitor: software that creates and runs virtual machines. A platform is everything wrapped around it like the guest, the snapshots, the orchestration, the density, and the team that keeps it patched. Here is exactly what that difference looks like. - Under 10 ms cold start for any workload - 100K+ microVMs per server - 10–100× better unit economics # A VMM does not make an entire platform Grab Firecracker and you get the isolation boundary. Everything above it (click a layer on the right to see what it does) is what you would otherwise design, build, operate, and patch yourself. The Unikraft platform provides the full stack: - **Deploy (BYOC, hosted, or on-prem) and get support:** Run the whole platform on bare metal or cloud VMs, deploy on-prem, bring-your-own-cloud, or on dedicated hosts. You own the full stack. SOC 2 and HIPAA compliant, with engineers on call. - **Kubernetes via Kraftlet virtual node:** Drop Unikraft into an existing EKS/GKE/AKS cluster as a node. Schedule ordinary pods, but have them run as strongly-isolated microVMs that scale to zero in 10 ms. - **Orchestration, autoscale, and live migration:** Scale to zero and statefully resume in under 10 ms. Spin up a fleet of new hosts in under 20 s to absorb spikes. Live-migrate running VMs across servers for HA and maintenance. - **Snapshot, fork, template, and checkpoint:** Branch a live VM and its children in ~10 ms. Spawn thousands of instances from a template. Take named, restorable checkpoints, rewind a running VM in place, and launch new VMs from any point in history — all in milliseconds. Upstream Firecracker has none of this at this granularity. - **Persistent shared storage:** Cluster-wide volumes shared seamlessly by VMs running on different servers. - **Guest OS (minimal Linux):** A Dockerfile becomes your own trimmed-down Linux kernel. The guest boots in a few ms. A stock Linux guest on raw Firecracker needs ~330 ms+ just to reach userspace. - **Hardened Firecracker fork:** The isolation boundary: a fast, minimal device model with VM-grade security. This one layer is exactly where "just grab Firecracker" stops — and even here we run a hardened fork. # What's actually included # Functionality, speed, density, reliability ## Speed — under 10 ms cold start Instant boot for any workload and instant scale-to-zero. - Cold-start any workload in under 10 ms — and scale to zero, then statefully resume, in under 10 ms. - The microVM guest boots in a few ms on top of the VMM. A stock Linux guest on raw Firecracker needs ~330 ms+ just to reach userspace. > "We took Go codebases from ~4 s startup with Docker on GCP to ~30 ms on Unikraft." > > — Matthew Anderson, ex-Equinix Metal ## Functionality — 10 ms to fork a live VM A full snapshot suite Firecracker doesn't have. - Fork a running VM (and its children) in ~10 ms - then spawn thousands of instances from a template. - Branch live workloads, take named checkpoints, rewind a VM in place, or launch new VMs from any point, all in millisecond timescales. - Turn any Dockerfile into your own minimal Linux microVM without rewrites, no wasm-specific changes. - Persistent shared storage, a plugin API, and custom filesystems across the cluster. ## Density & economics — 100K+ microVMs per server Density raw Firecracker alone won't give you. - Run 100,000+ strongly-isolated microVMs on a single standard server. - 10–100× better unit economics. > "We run over 100,000 strongly isolated PostgreSQL instances on a single machine." > > — Sören Schmidt, CEO, Prisma ## Reliability — under 20s to add a full host - Live-migrate running VMs across hosts for HA, maintenance, re-balancing, and spot instances. - Autoscale a fleet of new hosts in under 20 s for spikes — and scale back to zero when idle. - Run as a node in your existing k8s cluster (EKS/GKE/AKS) via Kraftlet — pods run as strongly-isolated microVMs. - SOC 2 Type II and HIPAA compliant. Deploy on-prem, BYOC, or dedicated — you own the full stack, with engineers on call. # Our Firecracker isn't the one you'd grab. If you grab the open-source VMM you will inherit the roadmap and the CVE queue. We maintain a large fork of Firecracker, and it ships on a monthly cadence. [Release 11 "Metis"](/blog/metis-11-release) of our platform, just by itself, added branching & checkpointing, custom filesystems, a plugin API, and a network shield. **Snapshotting & state** — Branch a live microVM (memory + volumes) with ~ms of downtime, or take named, restorable checkpoints. Custom filesystems give agents state that follows the work across the cluster. **Networking & the shield** — VPC-style multi-interface networking, plus a transparent network shield: a separate scale-to-zero microVM that filters traffic and injects secrets — so untrusted workloads never hold a secret or get unfiltered egress. **The plugin API** — Transparently extend a running microVM with your own code over an authenticated channel — in-VM command execution and filesystem services, no unauthenticated service exposed. It powers the native sandbox. **Platform & operations** — A rebuilt dashboard with real-time metrics and logs, automatic disk reclamation, richer health checks for drain/upgrade workflows, and always-current online enterprise docs. Also in the platform — more you'd otherwise build: GPU support, ARM, and dynamic vertical scaling (CPU & memory on the fly). ## Don't rebuild the platform. Deploy on it.

VM-grade isolation, 10 ms cold starts, and 100K+ instances per server — on-prem, BYOC, or dedicated. No setup, no commitment.

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