← Back to list
Job · Principal

Principal Research Engineer

AI / ML Engineer • Principal • Remote • Full-time • 📍 Europe

Synthesia is the world's leading AI video platform for business, used by over 90% of the Fortune 100. Founded in 2017 and headquartered in London, with offices across Europe and the US. After a Series E round raising $200M, its valuation stands at $4B. As a Principal Research Engineer (L7) you own the full technical stack for offline, human-centric video generation - a senior individual contributor role bridging pre-training and post-training, spanning roughly 15 people. You partner with research leadership to define long-term strategy, resolve the hardest cross-cutting problems and accelerate how quickly research reaches product. The role is remote in Europe.

Stack

Responsibilities

  • Own the end-to-end technical direction for offline video generation across pre-training and post-training
  • Partner with research leadership and team leads to define a unified long-term roadmap and drive execution
  • Identify the most critical technical gaps across the pipeline and unblock them (architecture, training stability, post-training alignment, cross-team coordination)
  • Increase the velocity at which research ships to product and improve research-to-production handoffs in partnership with PMs
  • Coach and elevate junior researchers and engineers toward senior technical thinking and execution
  • Help shape team structure and refine processes for high-velocity, cohesive execution

Requirements

  • Proven track record training large-scale video generation models from scratch, across multiple nodes, at the scale of millions of hours of data
  • Deep experience with post-training techniques at scale: RLHF, GRPO, DPO, with the judgment of when and how to apply them
  • Proven track record with data quality and willingness to question it
  • Ability to think strategically about multi-year research direction while executing hands-on at the frontier
  • Strong cross-functional influence without needing positional authority
  • Leadership style grounded in technical involvement - leads by example and communicates with clarity
  • Genuine hunger to unlock new capabilities and an obsession with shipping

Nice to have

  • Having owned a major model generation or capability jump end-to-end, from training runs to product deployment
  • Working across both pre-training and post-training stages on the same model family with accountability for both
  • Operating at scale: large distributed training runs, significant compute budgets, multi-million hour data pipelines
  • Applying alignment and fine-tuning techniques in a video or multimodal context, not just text
  • Experience with human feedback pipelines applied to generative video or audio
  • Leading or significantly influencing the technical direction of a research team while remaining hands-on

Soft skills

Clear and direct communication across research and productLeads by example and inspires through craftStays personally present at the hardest parts of the work