Staff Machine Learning Engineer, Ads Foundational Representations

• Join the Ads Foundational Representations team, which develops signals and representations of Reddit’s core entities including ads, posts, and users. • Capture the semantic, contextual, and behavioural information Reddit Ads needs, building embeddings that understand content and user interests. • Work across multimodal and content embeddings, contextual and behavioural relevance, knowledge graph embeddings, user intent modelling, and LLM-based representations. • Build signals and features that become a key piece of the Ads Delivery funnel, from targeting to the auction, plus Business Insights and advertiser-facing products. • Set the technical direction for multiple pillars the team owns. • Lead cross-functional ML projects end to end, from high-level business gap analysis through engineering execution. • Split your time roughly 50/50 between technical leadership and mentorship, and hands-on individual work across data analysis, engineering, modelling, and automation. • Work remotely from anywhere in the UK, as Reddit is a flexible-first workforce.

• Bring 7+ years of hands-on experience across the full lifecycle of designing, training, evaluating, testing, and deploying industry-level models. • Demonstrate staff-level technical leadership: mentoring engineers, driving standards, and leading complex cross-functional projects from requirements through design, alignment, and execution without direct people-management authority. • Communicate excellently, translating complex technical concepts for different audiences in writing and in person. • Bring a strong track record working on content-rich NLP or computer vision problems at scale, using embeddings as a tool to solve them. • Bring an established data-driven approach to ML system development, with a readiness to look behind the metric numbers. • Bring familiarity with the ads domain, or with search and recommender systems. • Bring experience with mainstream deep learning frameworks, either PyTorch or TensorFlow.

• Bring experience with Reddit’s stack: Python, PyTorch, Airflow, BigQuery, Ray, Kubernetes, Kafka, and GCP. • Bring tech leadership experience mentoring junior engineers and leading complex projects. • Bring hands-on experience using, fine-tuning, or building LLMs. • Bring experience with two-tower architectures and sequence models. • Bring experience developing evaluation methodologies for large models. • Let your recruiter know if you need an accommodation during the interview process due to a disability.

• Provide technical leadership and mentorship to MLEs on the team, driving designs and their review and establishing best practices across analysis, modelling, and engineering. • Work with team and org leadership to develop the technical strategy for content-based embeddings and relevance for Ads. • Develop new embedding models and iterate on existing ones for advertising use cases, from aggregation pipelines to two-tower architectures and sequence models. • Work with local and third-party LLMs and VLMs to extract representations, develop evaluation methodologies, and prompt tune and fine-tune large models. • Build data processing and inference pipelines for the models the team develops. • Evaluate features qualitatively and quantitatively, running end-to-end experimentation from internal benchmarks through offline recommender metrics to online experiments. • Ensure the reliability, scalability, and performance of ML systems through automated tests, performance monitoring, and model management best practices. • Review modelling and code from other team members, giving feedback that holds the team’s quality bar. • Collaborate with cross-functional teams to translate business requirements into technical solutions.

• Work remotely from anywhere in the UK, with no office requirement. • Access global benefit programs covering workspace, professional development, and caregiving support. • Use family planning support and generous paid parental leave. • Access gender-affirming care. • Use mental health and coaching benefits. • Join a group personal pension scheme with employer match. • Access private medical and dental schemes and income replacement programs. • Join the bike to work scheme. • Take flexible vacation and paid volunteer time off. • Stay hands-on while setting technical direction, with the role split evenly between leadership and individual work.

Reddit is a community of communities, built on shared interests, passion and trust, and home to some of the most open and authentic conversations on the internet. Every day its users submit, vote and comment on the topics they care most about. With more than 100,000 active communities and approximately 130 million daily active unique visitors, Reddit is one of the internet’s largest sources of information.