Principal Applied Research Engineer – AI Video Generation

About the role

Synthesia's video generation capability is core to everything we ship. We are looking for a Principal Research Engineer (L7) to own the full technical stack for offline video generation. This senior individual contributor role partners directly with research leadership and team leads to define long‑term strategy, solve cross‑cutting technical challenges, and accelerate the path from research to product.

Key responsibilities

• Own the end‑to‑end technical direction for offline video generation, spanning pre‑training and post‑training, and remove artificial boundaries between stages.
• Partner with research leadership and team leads to define a unified long‑term roadmap, break it into achievable objectives, and drive execution.
• Identify critical technical gaps across the video generation pipeline and intervene on architecture, training stability, post‑training alignment, or cross‑team coordination.
• Increase the velocity at which research ships to product by accelerating problem‑solving, improving handoffs, and raising visibility of research output with product managers.
• Coach and elevate junior researchers and engineers toward senior technical thinking and execution.
• Help shape team structure and refine processes to enable high‑velocity, cohesive execution across research.

Required profile

• A proven track record training large‑scale video generation models from scratch across multiple nodes and millions of hours of data.
• Deep experience with post‑training techniques at scale such as RLHF, GRPO, and DPO, and the judgment to apply them appropriately.
• Strong focus on data quality and willingness to question it.
• Strategic thinking about multi‑year research direction combined with hands‑on execution at the frontier.
• Cross‑functional influence without needing positional authority.
• Leadership style grounded in technical involvement, leading by example and communicating clearly.
• Genuine hunger to unlock new capabilities and an obsession with shipping research into user‑facing products.

Required skills

• RLHF
• GRPO
• DPO