Senior Multilingual Data Engineer & ML Researcher

Reflection AI; San Francisco, New York (CA, NY); On-site; USD 150,000 - 210,000; Full time

Job summary

Reflection AI is seeking a talented engineer to design, operate, and evolve large-scale multilingual data pipelines for language modeling. You will source, clean, deduplicate, identify languages, and normalize scripts across many languages, with a focus on quality and cultural fidelity.

You will lead small research projects, run experiments, and build evaluation sets to diagnose where model behavior falters. A strong measurement mindset and teamwork are essential.

Qualifications

• Strong software engineering fundamentals and comfort processing web-scale datasets in distributed environments.
• Experience building large-scale data pipelines for language models, machine translation, speech, or search — ideally covering more than one language.
• Fluency or working proficiency in at least one language other than English, and genuine curiosity about how languages differ.
• A rigorous, measurement-first mindset: you prove a data change helped rather than assuming it did.
• Navigate trade-offs between research objectives and practical engineering realities.
• Comfortable with ambiguity and high ownership in a small, fast-moving team. Passionate about advancing the frontier of intelligence.

Responsibilities

• Design and operate large-scale multilingual data pipelines — sourcing, cleaning, deduplication, language identification, and script normalization across high- and low resource languages.
• Define and enforce quality bars for multilingual corpora, including translation quality, cultural fidelity, toxicity, and contamination checks.
• Design and run scientific experiments to advance our understanding of scaling large language models to improve multilingual data efficiency.
• Lead small research projects independently while collaborating on larger initiatives.
• Build evaluation sets and diagnostics that expose where model behavior degrades by language, register, or domain, and close those gaps with targeted data.
• Work with pre-training, mid-training, and post-training teams to land measurable, step-function improvements in multilingual capability.

Skills

Software engineering fundamentals

Distributed data processing

Multilingual NLP data pipelines

Measurement-driven mindset

Ambiguity tolerance

Education

MS/PhD in Computer Science or Machine Learning

Job description

Reflection AI is seeking a talented engineer to design, operate, and evolve large-scale multilingual data pipelines for language modeling. You will source, clean, deduplicate, identify languages, and normalize scripts across many languages, with a focus on quality and cultural fidelity.

You will lead small research projects, run experiments, and build evaluation sets to diagnose where model behavior falters. A strong measurement mindset and teamwork are essential.