Member of Technical Staff - Research Software Engineer in London

Reflection’s mission is to build open superintelligence and make it accessible to all. We’re developing open weight models for individuals, agents, enterprises, and even nation states. Our team of AI researchers and company builders come from DeepMind, OpenAI, Google Brain, Meta, Character.AI, Anthropic and beyond.

Responsibilities

• Bridge the gap between research and production by turning cutting-edge algorithms into scalable training systems.
• Design and optimize the core infrastructure behind frontier AI models — from reinforcement learning training loops and distributed GPU training to massive-scale data pipelines.
• Our systems train models across thousands of GPUs and process petabyte-scale datasets.
• This team owns and evolves the core infrastructure behind our training systems.

We Focus On

• Reinforcement learning training infrastructure
• Distributed training and inference systems
• Experiment infrastructure and reproducibility
• Large-scale data pipelines

The goal is to build the engineering foundation that allows researchers to iterate quickly while training models at massive scale.

About The Role

You will architect and optimize the core training infrastructure that powers our models. This includes RL training loops, distributed GPU systems, and large-scale data pipelines. You will work closely with researchers to transform new ideas into reliable, scalable training systems.

Responsibilities Include

• Designing and optimizing large-scale training loops and data pipelines.
• Implementing state-of-the-art techniques and ensuring they are numerically stable and computationally efficient.
• Building internal tooling for launching, monitoring, and reproducing complex experiments.
• Diagnosing deep bottlenecks across the training stack (GPU memory issues, communication overhead, dataloader stalls).
• Translating research prototypes into reusable, production-grade infrastructure.

What You’ll Work With

• Distributed Training

• GPU parallelism (data, tensor, pipeline, expert)
• Large-scale distributed training infrastructure
• Communication optimization (NCCL, RDMA, GPU interconnects)
• FSDP / ZeRO and model sharding

• Ray, Kubernetes, Slurm
• Distributed runtimes and async systems
• Containerization and sandboxing

• PyTorch
• JAX
• Megatron-style training stacks
• Triton / custom kernels

• Large-scale dataset curation pipelines
• Deduplication and filtering systems
• Tokenization and preprocessing
• Distributed data processing frameworks

About You

• You are a strong software engineer who speaks the language of machine learning.
• You may not have a PhD, but you know how to implement a research paper.
• You have deep experience in at least one of the following: Distributed Training & Inference or Data Infrastructure.
• You enjoy working at the boundary between:

• Machine learning algorithms
• Distributed systems
• High-performance computing

What We Offer

• Top-tier compensation: Salary and equity structured to recognize and retain the best talent globally.
• Health & wellness: Comprehensive medical, dental, vision, life, and disability insurance.
• Life & family: Fully paid parental leave for all new parents, including adoptive and surrogate journeys. Financial support for family planning.
• Benefits & balance: paid time off when you need it, relocation support, and more perks that optimize your time.
• Opportunities to connect with teammates: lunch and dinner are provided daily. We have regular off-sites and team celebrations.