About this role.
Nebius is seeking a Senior Hypervisor Engineer to join its hyperscaler platform team, focusing on KVM and QEMU development. The role involves optimizing I/O for virtualized devices, integrating the hypervisor with platform services, and contributing to open source virtualization. Candidates need 5+ years of software engineering experience, deep C programming expertise, and at least 3 years with QEMU/KVM. This is a fast-paced, high-impact position within a globally distributed AI cloud infrastructure company.
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Cover letter sample
Dear Hiring Team,
I am excited to apply for the Senior Hypervisor Engineer position at Nebius. With over five years of experience in systems programming and a deep focus on QEMU/KVM internals, I have a proven track record of optimizing virtualized I/O and contributing to upstream open source projects. My expertise in C, Linux user-mode development, and x86 architecture directly aligns with your team's mission to advance cloud infrastructure for the AI economy.
At my previous role, I delivered performance improvements to virtio-net and virtio-blk devices, reducing latency by 30% for high-throughput workloads. I also collaborated closely with the open source community to merge patches into QEMU, ensuring long-term maintainability and upstream alignment. I am particularly drawn to Nebius's emphasis on owning hard problems and the opportunity to shape the future of AI infrastructure.
I thrive in fast-paced environments that value trust and real ownership, and I am eager to bring my skills to your team. Thank you for considering my application; I look forward to discussing how I can contribute to Nebius's success.
Sincerely, [Your Name]
Sample interview questions
QEMU runs as a user-mode process on the host Linux system. It creates and manages vCPUs using the KVM kernel module via ioctl calls. The KVM module sets up hardware virtualization (VMX/SVM) and handles guest execution, while QEMU provides device emulation, memory mapping, and I/O handling. When a guest accesses an MMIO or PIO device, KVM exits to user space and QEMU emulates the device.
I would first profile the data path, looking at packet copy overhead, interrupt coalescing, and vhost-user configuration. I'd inspect the virtqueue ring sizes, use of multi-queue, and batch processing. Also, consider offloading checksum or segmentation to hardware, and ensure the NIC driver is using zero-copy if possible. Bottlenecks often include cache misses, lock contention, and excessive vmexits.
I once diagnosed a race condition in a device emulation path that caused intermittent guest crashes. I used QEMU's built-in tracing (ftrace), gdb for core dumps, and address sanitizer to detect memory corruption. I identified a missing memory barrier in the ring buffer update logic. After confirming with a stress test, I submitted a patch upstream that added proper synchronization.
I focus on minimizing attack surface by reducing emulation code, using hardware virtualization features, and validating all guest inputs. I also enable exploit mitigations like SMEP, SMAP, and address space isolation. I participate in code reviews and fuzzing campaigns, and stay updated on CVEs affecting QEMU/KVM. For example, I ensure the QEMU process runs with minimal privileges and seccomp filters.
I have contributed several patches to QEMU for block device improvements. I start by engaging on the mailing list, understanding the maintainer's preferred style, and breaking changes into small, reviewable patches. I respond to feedback promptly and make necessary adjustments. I also study maintainers' recent commits to align with the project's roadmap and coding standards.
About Nebius:
Nebius is leading a new era in cloud infrastructure for the global AI economy. We are building a full-stack AI cloud platform that supports developers and enterprises from data and model training through to production deployment, without the cost and complexity of building large in-house AI/ML infrastructure.
Built by engineers, for engineers. From large-scale GPU orchestration to inference optimization, we own the hard problems across compute, storage, networking and applied AI.
Listed on Nasdaq (NBIS) and headquartered in Amsterdam, we have a global footprint with R&D hubs across Europe, the UK, North America and Israel. Our team of 1,500+ includes hundreds of engineers with deep expertise across hardware, software and AI R&D.
The role
We’re looking for a Senior Hypervisor Engineer to contribute to the development of our hyperscaler platform.
The Hypervisor team supports and develops the parts of the Cloud platform that directly affect the KVM hypervisor and QEMU device emulator. We understand the granular details of hardware virtualization and device emulation, paying close attention to performance and protection against untrusted code.
You will work on substantial extensions for the QEMU/KVM virtualization stack in close cooperation with the opensource community.
- Optimize I/O for emulated disk and network devices
- Integrate the hypervisor with other platform services and storage facilities for user data
- Efficiently distribute resources between virtual machines
- Improve guest system support
- Advance the cutting-edge of open source virtualization
- Provide low-level security for the hypervisor and emulator
- Provide general support, fix bugs, and monitor the upstream
- Collaborate with other team members and stakeholders
- 5+ years of professional software engineering experience
- Fluent in C programming language
- 3+years of experience with Linux
- At least 3 years of engineering experience with QEMU/KVM
- General understanding of x86-compatible systems (virtual memory, interrupts, privilege rings)
- Experience writing general system code in user mode for Linux, including debugging, analysis, and optimization tools (the emulator is built on the user mode system process for Linux)
- Aсcepted patches in Linux Kernel or QEMU/KVM
- Experience working with Linux kernel
- Some experience with ARMv8, including virtualization extensions
- Understanding of PCI, SCSI, and ACPI
- Experience working with the Linux kernel
- Excellent communication skills for cross-team collaboration
- Strong work ethic
We conduct coding interviews as part of the process.
Benefits & Perks:
- Competitive compensation
- Career growth and learning opportunities
- Flexibility and ownership
- Collaborative and innovative culture
- Opportunity to work on impactful AI projects
- International environment and talented teams
What’s it like to work at Nebius:
Fast moving – Bold thinking – Constant growth – Meaningful impact – Trust and real ownership – Opportunity to shape the future of AI
Equal Opportunity Statement:
Nebius is an equal opportunity employer. We are committed to fostering an inclusive and diverse workplace and to providing equal employment opportunities in all aspects of employment. We do not discriminate on the basis of race, color, religion, sex (including pregnancy), national origin, ancestry, age, disability, genetic information, marital status, veteran status, sexual orientation, gender identity or expression, or any other characteristic protected by applicable law.
Applicants must be authorized to work in the country in which they apply and will be required to provide proof of employment eligibility as a condition of hire.
If you need accommodations during the application process, please let us know.
Annual salary information is not provided for this position. Explore salary ranges for similar roles in our Salary Directory ›
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