# Platform Security Engineer at Fly.io

Fly.io is hiring a Platform Security Engineer for a remote role open to applicants in United States. It pays $180k-$225k a year and Level rates it Little AI ●○○○; you can [apply on Fly.io](https://jobsbylevel.com/go/c1c09dee-00d5-4676-8c9e-0c34b9eebad3?utm_medium=ai-agent).

AI Level 1, AI centrality 32 out of 100. Remote (Remote).

## Details

- Company: [Fly.io](https://jobsbylevel.com/companies/fly)
- AI level: AI Level 1 (score 32 out of 100)
- Location: Remote (Remote)
- Salary: $180k-$225k
- Posted: November 5, 2026
- Apply: https://jobsbylevel.com/go/c1c09dee-00d5-4676-8c9e-0c34b9eebad3?utm_medium=ai-agent
- Free CV review for this job: https://jobsbylevel.com/cv-review?job=platform-security-engineer-at-fly-7edee5

## Description

About Fly.io We're building a public cloud that runs on our own hardware all over the world. Customers hand us containers; we convert them into micro-VMs under hardware virtualization, each with its own kernel, on thousands of bare-metal hosts we operate ourselves. A growing share of those workloads are AI agents and inference, which means a growing share of the people attacking cloud platforms are interested in us. Isolation is the product. The boundary between one customer's workload and the next, and between any workload and our own control plane, is a stack of things we build and run: the VMMs and their jailers, seccomp filters, host networking rules, the identity each host presents to the rest of the fleet, and the custom kernel underneath all of it. When that boundary holds, nobody notices. That's the job. The Role We have a security team. It covers application security, trust boundaries and auth, vulnerability research against our own hypervisor stack, corporate security, compliance, and disclosure. What it doesn't have is someone who works alongside the platform team hacking on the platform itself: the kernel, the hypervisor jailers, the syscall filters, host network isolation, and the trust relationships between hosts. That's the gap this role closes. The work has two halves, and you will own both: Keep the guest in the VM. Harden the per-workload boundary on every host. Plan for the worst. Limit the blast radius for when the next horrible KVM guest-to-host escape drops. You will report to the Head of Security, who will set your priorities and review your work, but you will spend most of your day with the Platform team, who own the systems you will be changing. Coordination and communication will be just as important as raw technical skills. What You'll Be Doing Isolation and sandboxing. We run two VMMs, Firecracker and Cloud Hypervisor, with jailers around them. You will own the syscall filtering, the process-level confinement, the network confinement around the jailers, and the violation telemetry that feeds our detection pipeline, across both VMMs and the host services that make up the platform. Host network isolation. A lot of our fleet's isolation rests on nftables and friends. You will own what each host is allowed to talk to, by role, and the health checks and killswitches that tell us the rules in force are the ones we intended. Blast radius and control-plane trust. The second half of the job. You will own the trust model between hosts and the control plane: how a host identifies itself and how its actions are attributed, how host-to-host operations such as machine migration are authorized, which services run on hosts that also run customer workloads, and what credentials live on a host and what each one can reach. You will design this with the Platform and Networking teams, build the host-local pieces yourself, and verify the rest. The kernel. We build and patch our own host kernel. You will own the patching cadence and its SLA, keep kernel expertise spread across the fleet team rather than concentrated in one person, and own live kernel patching for the fixes that cannot wait for a reboot cycle. Agent workloads. The platform increasingly runs agents, including a sandbox product for them. You will take the isolation half of that design seat: VMM confinement, worker-side controls, and what the platform can honestly guarantee an agent workload. This may even include compute where we no longer own the metal, and we will need to design for a fleet that spans trust levels. When it breaks. A suspected guest escape, a host behaving strangely, weird kernel behavior: these need someone who can lead the technical investigation on the host, not just coordinate it. You will be one of the names we call, and you will help strengthen our forensics playbook. You will want to be comfortable working with coding agents. We lean on them hard, and the honest truth of low-level security work is that an agent will confidently hand

The description is cut here. Read the full offer: https://jobsbylevel.com/jobs/platform-security-engineer-at-fly-7edee5

Source: https://jobsbylevel.com/jobs/platform-security-engineer-at-fly-7edee5

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