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Bell Labs internship on Hot-Swappable JIT Compilation for Faster Cold Starts (PhD)

Nokia

Nokia

Belgium
Posted on Dec 12, 2025

Modern runtimes (JavaScript, WebAssembly) rely on multi-tier JITs to combine fast startup with optimized performance. However, cold-start compilation and repeated re-optimization still incur significant cost overhead, especially in browsers, serverless platforms, and mobile environments.

This internship explores hot-swappable JIT-compiled code sections: externally pre-optimized fragments (e.g. on the server) that can be safely injected into an active interpreter or baseline JIT (e.g. in the browser). The goal is to reduce redundant compilation, accelerate cold starts, and evaluate tradeoffs between de-optimization and execution behavior.

A key challenge is how to maintain the security and sandboxing guarantees of these environments. Hence, we envision a need to define secure patchpoints, security mechanisms, and interfaces between the interpreter, baseline JIT, and injected optimized code.

A prototype can target JavaScript or WebAssembly (or others), using custom interpreters or existing open-source JIT infrastructures.

Duration: flexible, to be agreed (typically 3-5 months), starting time flexible.


Advancing connectivity to secure a brighter world.

Nokia is a global leader in connectivity for the AI era. With expertise across fixed, mobile and transport networks, powered by the innovation of Nokia Bell Labs, we’re advancing connectivity to secure a brighter world.



About the Business Group

The Strategy and Technology organization drives Nokia’s future innovation by identifying value-creation opportunities, setting a unified company vision, and developing coherent business, technology, and architecture strategies. It establishes a research foundation for new products and solutions while providing critical infrastructure to support secure and effective execution across all Nokia business units.

Nokia Bell Labs, the world-renowned industrial research arm of Nokia has pioneered breakthrough foundational technologies over the past 100 years like the transistor, laser, Unix, and solar cell - shaping modern communications, computing and connectivity. Today, it drives innovation in AI, quantum computing, 6G, and space communications, bridging groundbreaking research to real-world applications with meaningful impact on society. With ten Nobel Prizes and five Turing Awards, Nokia Bell Labs continues to define the future of technology.


Our recruitment process

We act inclusively and respect the uniqueness of people. Our employment decisions are made regardless of race, color, national or ethnic origin, religion, gender, sexual orientation, gender identity or expression, age, marital status, disability, protected veteran status or other characteristics protected by law. We are committed to a culture of inclusion built upon our core value of respect.

If you’re interested in this role but don’t meet every listed requirement, we still encourage you to apply. Unique backgrounds, perspectives, and experiences enrich our teams, and you may be just the right candidate for this or another opportunity.

The length of the recruitment process may vary depending on the specific role's requirements. We strive to ensure a smooth and inclusive experience for all candidates. Discover more about the recruitment process at Nokia.

Some of our benefits:
  • Flexible and hybrid working schemes
  • Well-being programs to support your mental and physical health
  • Opportunities to join and receive support from Nokia Employee Resource Groups (NERGs)
  • Employee Growth Solutions to support your personalized career & skills development
  • Diverse pool of Coaches & Mentors to whom you have easy access
  • A learning environment which promotes personal growth and professional development - for your role and beyond


Design and prototype hot-replaceable AOT/JIT-compiled JavaScript / WebAssembly code to reduce energy usage and improve cold start time. #compiler #just-in-time #zero-knowledge-proof #cryptography #javascript #webassembly
  • Student enrolled in Ph.D. Computer Science/Engineering.
  • Solid background in compilers, JITs, interpreters, optimizers, or runtime systems.
  • Strong programming skills, preferably in C, C++, or Rust.
  • Language skills: English

  • Build upon an existing (open source) JavaScript or WebAssembly runtime to pre-optimize “likely hot” code fragments.
  • Explore mechanisms to maintain safety and sandboxing guarantees.
  • Evaluate the trade-offs in performance gain (due to the optimization), proving time (for asserting correctness ahead of time), and verification time (for verifying safety during execution).
  • Apply your research to a practical problem.
  • Potential for a scientific publication with Bell Labs researchers.