Member of Technical Staff - Multilingual Data

Reflection • London, California

6d • Onsite

About The Position

Reflection is a research lab focused on making intelligence open and accessible. This role involves designing and operating large-scale multilingual data pipelines, defining and enforcing quality standards for multilingual corpora, and conducting scientific experiments to improve multilingual data efficiency for large language models. The position requires building evaluation sets to identify and address model performance gaps across different languages and domains, and collaborating with various teams to enhance multilingual capabilities.

Requirements

• 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.

Nice To Haves

• Graduate degree (MS or PhD) in Computer Science, Machine Learning, or related discipline.
• Published work in multilingual NLP, low-resource languages, or evaluation methodology.
• Experience with annotation vendor management or crowdsourced data operations at scale.
• Familiarity with tokenizer design and its effects on non-Latin scripts.

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.

Benefits

• Top-tier compensation: Salary and equity structured to recognize and retain our talent globally.
• Stock options: Everyone who joins and contributes to Reflection's success gets to share in the upside through stock options.
• Health & wellness: Comprehensive medical, dental, vision, and life, with an annual wellness allowance.
• Meals: Lunch and dinner are provided in the office daily.
• Life & family: 22 weeks paid parental leave for all new birthing and non-birthing parents, including adoptive and surrogate journeys.
• Vacation days: Unlimited paid time off in the U.S. and 30 days in the U.K.
• Sponsorship support: We sponsor visas to help exceptional talent join our team and support long-term immigration pathways where applicable.
• Team building: We have regular off-sites, happy hours, and team celebrations.

What This Job Offers

• Job Type: Full-time
• Career Level: Mid Level