Senior Machine Learning Engineer, Tumblr

Tumblr launched in 2007 with the belief that people need a place to say what they want, be who they want, and connect over their interests. We continue to build Tumblr as a platform for free expression, individuality, and human connection.

We are looking for an experienced candidate to join our Feeds Experience team, which builds Tumblr's backend systems—powering core content feeds, search, personalization/discovery experiences, user-interest profiling, content understanding and notifications. Your goal will be to design, develop and maintain large-scale data pipelines and backend services, to connect users with the content they love. The team plays a critical role in driving daily active users by improving engagement and retention on Tumblr.

We build on top of open source big-data frameworks, such as Apache Spark (batch processing) and Apache Flink (real-time processing), orchestrated by Kubernetes, Apache Airflow, and with a PHP backend layer.

Responsibilities:

• Collaborate with the team to enhance engagement on feeds, notifications, content discovery and relevance of search results.
• Research and develop new features to improve user engagement and the reactivation of lapsed users.
• Define success metrics, launch A/B tests, perform analysis to validate hypotheses, and build tools to enable continuous experimentation.
• Contribute to the team's strategy and roadmap, including identifying opportunities for business impact, driving architectural decisions, and quantifying the impact of implemented solutions.

Requirements:

• Good understanding of statistics, machine learning, and mining of massive datasets.
• 3+ years of professional experience developing large-scale data-pipelines and machine learning approaches for content retrieval, ranking, relevance, and personalization.
• 5+ years of professional experience in software engineering, with expertise in Python, Scala, or Java.
• Hands-on experience with data processing frameworks like Apache Spark and Apache Flink at scale.
• Excellent written English and effective communication skills.
• Goal-driven, humble, and willing to learn and teach.
• Excitement to join a globally distributed team.

What will make you stand out:

• MS/PhD in Computer Science, ML, or related fields.
• Experience in large-scale notifications systems for driving user growth and engagement loops.
• Deep expertise in search ranking and relevance at scale, particularly with Elasticsearch.
• Experience in embedding-based recommendation and retrieval.
• Experience in real-time stream processing frameworks.

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