Blog — page 27 of 38
Per-Tenant Feature-Flag Evaluation in microVMs
A tenant's "harmless" targeting rule that turns out to be while(true) shouldn't take down flag evaluation for everyone. Run each tenant's rules in its own capped microVM and the blast radius stops at one VM.
Quarantine Flaky Tests with Ephemeral MicroVMs
"It passed on retry" is not a fix — it's a shared, dirty runner leaking state between tests. Give each run a fresh microVM, then fork one flaky test N ways to measure its real flake rate.
Sandboxing AI-Agent Spreadsheet Automation
"quarterly_report.xlsx" is a file format that can phone home, fork-bomb your converter, and run pandas code an LLM wrote five milliseconds ago. When your agent transforms user spreadsheets, give each job its own disposable microVM.
Isolating Multi-Tenant GenAI Image Jobs in MicroVMs
A GenAI image platform runs custom ComfyUI graphs, pip-installed model nodes, and user-uploaded checkpoints that are effectively untrusted pickled code. One poisoned .safetensors on a shared box reads every neighbor. One microVM per job fixes it.
Firecracker vs CheerpX / WebVM: where does the code run?
CheerpX/WebVM runs a whole Linux distro inside the browser tab with zero backend; Firecracker runs a real microVM on your server. They solve opposite problems — here's the honest split.
Guest Clock Drift After a Firecracker Snapshot Restore
Restore a snapshot from last Tuesday and the guest still thinks it's last Tuesday. That frozen wall clock quietly breaks TLS, JWTs, cron, and rate limiters — until you step it back to now on restore.
Firecracker's seccomp-BPF filters explained: locking down the VMM's own syscalls
A container is a polite suggestion to the kernel; a seccomp filter is the kernel finally saying no. Firecracker points that 'no' at itself — the VMM allowlists only a few dozen host syscalls, so a guest that breaks out lands in a straitjacket, not a shell.
Firecracker vhost-user-block Devices Explained
Firecracker's built-in virtio-block device emulates storage inside the VMM process. vhost-user-block does the opposite: it hands the datapath to a separate backend process over a Unix socket, sharing the guest memory and virtqueues with it. That decoupling is how you plug in a custom, networked, or demand-paged block backend without bloating the VMM — and the trade is one more process you have to trust. Here's how it actually works.
Best Secure Sandboxes for LLM Agents in 2026
When an agent runs model-generated code, the isolation model is the product. A security-first roundup ranked by the strength of the boundary — microVM, gVisor, Kata, containers, WASM — plus the operational hygiene that keeps it real.
A Production Checklist for Running Untrusted Code Safely
You're about to run code you didn't write and can't review — a user submission, a build script, a shell command your model just emitted. Here's the operational checklist: ten items, each explained, that decide whether a hostile run is a deleted VM or an incident report.
Give Your AI Agent a Terminal — Not Yours
An AI agent that runs shell commands needs a real terminal. Give it a disposable Firecracker microVM instead of a subprocess on your box — where sudo rm -rf / is a shrug.
Run AI-Agent DB Migrations in an Isolated microVM
You let a model generate a migration. It's confident. It says DROP TABLE users; -- oops. Run that against a disposable Postgres inside a microVM, not your real database.
Isolating AI-Agent Mobile App Builds in a MicroVM
An AI agent that builds mobile apps runs npm install and gradle assembleRelease on dependency trees you never audited — and postinstall scripts run as your build user. Give each build its own throwaway microVM.
Per-Tenant Isolation for User-Defined GraphQL Resolvers
Your headless CMS lets customers write GraphQL resolvers in JS or Python. That's arbitrary tenant code on your request path. Here's how to isolate it per tenant without blowing the latency budget.
Firecracker vs nsjail: which for running untrusted code?
nsjail is a razor-sharp process jail for a known binary; Firecracker is a throwaway VM for arbitrary code. The difference is whose kernel the untrusted code gets to attack.
Firecracker vs Bubblewrap: sandboxing untrusted code
Bubblewrap is the unprivileged sandbox behind Flatpak — a brilliant filesystem jail on the host kernel. Firecracker gives a separate guest kernel. Here's where each one is the right call.
Firecracker CPUID masking, explained
The guest asks "do I have AVX-512?" and Firecracker gets to decide the answer. Here's why the hypervisor lies for its own good — and why snapshot portability depends on it.
Guest page cache: why it bloats microVM snapshots
A microVM snapshot captures the guest's RAM verbatim — including megabytes of file data Linux cached from a disk that's sitting right there. Drop the cache before you bake, and the memory image shrinks to the live working set.
Best Daytona Alternatives (2026): An Honest Roundup
The honest best-of for teams outgrowing Daytona: PandaStack, E2B, Modal, Northflank, Vercel Sandbox, Fly Machines/Sprites, Gitpod/Coder, and the OSS substrate — judged by decision criteria, not a leaderboard.
Snapshot vs restore vs fork vs clone, explained
Snapshot, restore, fork, clone — four words for branching a running VM's state that people use interchangeably and shouldn't. Here's what each one actually means.
Per-Tenant ML Inference Isolation With MicroVMs
A bring-your-own-model inference platform runs tenant B's pickle-loaded weights and Python preprocessing in the same worker that holds tenant A's data. That's cross-tenant RCE with extra steps. One microVM per tenant fixes it.
Sandbox Your Agent's Computer-Vision Pipeline in MicroVMs
Image and video libraries are a memory-safety minefield — ImageTragick, libwebp, malicious EXIF, decompression bombs. An agent decoding a stranger's upload in-process is asking for RCE. One microVM per job.
Per-Tenant ETL Pipeline Isolation With MicroVMs
Tenant B's custom Python transform runs in the same Airflow worker that holds tenant A's warehouse credentials. That's a cross-tenant data-exfiltration path with a friendly name. One microVM per pipeline run.
Firecracker vs E2B: You're Comparing Two Layers
"Firecracker vs E2B" is a category error people search for anyway. One is a VMM primitive; the other is a product built on that primitive. The honest comparison is build-vs-buy.