Principal VM Engineer - Workers Runtime Team

Available Locations: Aarhus, Denmark | Austin, TX | Lisbon, Portugal | London, UK | Munich, Germany Principal VM Engineer - Workers Runtime Team About the Department
The Emerging Technologies & Incubation (ETI) team at Cloudflare builds and launches bold, new products that push the boundaries of what's possible on the internet. By leveraging Cloudflare's massive network and edge computing capabilities, we solve complex problems at a scale few others can achieve.
About the Team
The Workers Runtime team is responsible for the execution environment that runs customer code at the edge. We focus on performance, security, and scalability, enhancing JavaScript APIs, WebAssembly support, and system optimizations to prepare for the next 10x scale increase. Our runtime operates in a resource-constrained, highly secure environment, requiring careful management of memory, CPU, and I/O.
What You'll Do
We are looking for a VM Engineer to help improve and embed the V8 virtual machine in our runtime. You'll work on low-level optimizations, performance enhancements, garbage collection, and language support to ensure our platform remains cutting-edge. This role is ideal for engineers who love tackling high-performance, low-latency challenges in distributed environments.
Key Responsibilities

• Optimize and embed the V8 VM within Cloudflare's Workers Runtime.
• Improve JavaScript execution performance and WebAssembly integration.
• Debug, optimize, and enhance low-latency, real-time environments.
• Ensure the reliability and efficiency of large-scale, Linux-based distributed systems.
• Collaborate with engineers across runtime, security, and networking teams to push the boundaries of edge computing.

What We're Looking For

• 6+ years of professional experience with C++.
• 4+ years of hands-on VM/compiler experience, ideally with V8.
• Strong knowledge of computer science fundamentals, including data structures, algorithms, and system architecture.
• Experience with low-latency environments (e.g., game streaming, trading systems, high-performance computing).
• Operational mindset - you build scalable, production-ready solutions.
• Deep understanding of web technologies (HTTP, JavaScript, WASM).

Bonus Points

• Experience working with Rust in high-performance distributed systems.
• Familiarity with serverless platforms and cloud computing.
• Deep knowledge of JS engine internals (V8, SpiderMonkey, JavaScriptCore).
• Experience with standalone WebAssembly runtimes (Wasmtime, Wasmer, Lucet).
• Strong expertise in Linux/UNIX systems, kernels, and networking.
• Contributions to large open-source projects.

This is an exciting opportunity to work on cutting-edge compiler and runtime technologies at an unmatched scale. If you're passionate about high-performance computing, distributed systems, and compilers, we'd love to hear from you!