Blog — page 36 of 38
seccomp explained for developers: filtering syscalls to shrink the kernel attack surface
seccomp lets a process pre-commit to the syscalls it's allowed to make; anything else gets killed or an errno. It's the bouncer at the kernel's door — and the second layer Firecracker stacks on top of KVM. But the bouncer isn't the building.
Best AI Agent Sandboxes in 2026
Where should your AI agent run the code and tool calls it generates? The honest field: PandaStack, E2B, Modal, Daytona, Vercel Sandbox, Fly Machines, and the build-it-yourself option — judged by criteria.
PandaStack vs Cloudflare Workers for Untrusted Code
Cloudflare Workers run JS/WASM in V8 isolates at the edge; PandaStack runs any binary in a Firecracker microVM. Different boundaries, different jobs.
vsock Explained: How the Host Talks to a microVM
How do you run exec, read files, and ping a sandbox for readiness without giving it a network or opening a port? You don't use TCP — you use vsock. Here's the CID/port model, the Unix-socket bridge Firecracker exposes, and how a guest agent rides it.
How to Jail LLM-Generated Code
The model is not malicious — it's just confidently wrong at root. Eventually it emits `rm -rf /`, an infinite loop, or a quiet exfil request. Here's how to jail every line of code it writes, layer by layer, with code you can paste.
How to Optimize MicroVM Cold Start
A cold start is a tax you pay on every create. The biggest cut isn't a faster boot — it's not booting at all. Here are six techniques to beat the microVM cold-start tax, ranked by impact, with the why behind each.
Run Untrusted MCP Servers in Isolated MicroVMs
Every MCP server you install is code you didn't write, running with access to your filesystem and network. The fix: one untrusted MCP server, one disposable microVM.
Preview Environments on microVMs: a Live URL per PR
Every pull request gets its own live URL backed by a real backend and database — on a Firecracker microVM, so even untrusted forked-PR code is isolated by hardware, not by a shared kernel.
Build an AI Data Analyst That Runs Code on User Data
Build a 'chat with your data' agent that runs model-written pandas and matplotlib over a user's own CSV — in a per-session microVM, with one tenant's data never touching another's.
Kata Containers vs Firecracker: Honest Head-to-Head
The framing is slightly off: Kata Containers is an OCI runtime that can run ON Firecracker. One gives you Kubernetes-shaped ergonomics, the other is the minimal VMM doing the isolating. Here's the honest comparison.
Firecracker vs Cloud Hypervisor: Picking a VMM
Same Rust lineage, shared crates, opposite philosophies. Firecracker keeps the device model microscopic for serverless density; Cloud Hypervisor adds the features general-purpose cloud guests need. Here's how to choose.
Best Firecracker Alternatives in 2026
If you like the microVM idea but want to compare VMMs — or skip running one entirely — here's the honest field: Cloud Hypervisor, QEMU, gVisor, Kata, Firecracker itself, and managed platforms.
How Firecracker Memory Snapshots Actually Work
A Firecracker snapshot is the guest's RAM, the VMM device state, and the rootfs. Restore maps the memory copy-on-write so the kernel pages it in lazily — which is exactly why you don't pay for the whole RAM image up front.
Safely Running Shell Commands an AI Agent Decides to Execute
The moment your agent can run `bash`, it can run anything bash can run. Command allowlists are a losing game — the model can base64, pipe to sh, or use $IFS. Here's the boundary that actually holds.
MicroVM Density: The Economics of Per-Tenant Isolation
Classic VMs were too heavy to give everyone one. MicroVMs change the density math — tiny per-guest overhead, shared copy-on-write memory, near-zero idle cost. Here's why per-tenant isolation is finally affordable.
KVM explained for developers: the hardware boundary under microVMs
You keep seeing "KVM" and "hardware virtualization" in isolation discussions. Here's the real mental model: a kernel module, the CPU's VT-x/AMD-V extensions, and the VM-exit trap that is the security boundary.
MicroVM Use Cases: What Firecracker Is Actually For (2026)
MicroVMs aren't a science project — they run AWS Lambda, agent code, CI jobs, and per-tenant databases. Here's where a Firecracker microVM actually earns its keep.
Firecracker Use Cases: Who Runs MicroVMs and Why
AWS built Firecracker to run Lambda. A decade later it's under AI code sandboxes, CI runners, and multi-tenant SaaS. Here's who runs microVMs, why — and when they're the wrong tool.
Serverless on Firecracker: How FaaS Really Works
Every "serverless" function is somebody's untrusted code running next to a stranger's untrusted code on shared hardware. That's a containment problem, and the industry's answer was microVMs. Here's how FaaS is really built — and why snapshot-restore is the part that matters.
Database-per-Tenant Isolation with MicroVMs
One tenant's runaway query shouldn't become everyone's incident. A tour of the multi-tenancy spectrum — shared schema, schema-per-tenant, database-per-tenant, VM-per-tenant — when full per-tenant DB isolation is actually worth it, and how a microVM makes it a clean boundary.
Browser Isolation in MicroVMs: Headless & Remote
A browser is a giant attack surface that executes arbitrary remote JavaScript — and now the model picks which links to click. Here's why one browser per disposable microVM is the clean answer for remote isolation and agent web automation.
Reproducible Builds in Disposable MicroVMs
A long-lived CI runner is a shared apartment where every previous tenant left something in the fridge. A fresh microVM per build is a hermetic, reproducible alternative.
Sandboxing LLM Tool Calls and MCP Servers
A tool call is the model reaching out of the chat and touching your systems. Here's how to box in function calling, MCP servers, and computer use so a hijacked call destroys a throwaway VM, not your infra.
MicroVM vs VM vs Container: A 2026 Comparison
A traditional VM gives you strong isolation and a heavy bill. A container gives you density and a shared kernel you're trusting with your life. A microVM is the third option — VM-grade isolation at near-container speed. Here's the honest three-way.