Senior Machine Learning Engineer Ii, Search & Recommendations Ranking

Instacart Instacart · Consumer · San Francisco, CA · Machine Learning

Instacart is seeking a Senior Machine Learning Engineer II for their Search & Recommendations Ranking team. This role focuses on building and optimizing the foundational ranking backbone that powers the entire shopping journey, aiming to improve metrics beyond clicks, such as GTV, basket lift, and retention. The position involves architecting multi-task/multi-objective models, designing value-aware optimization systems, and enhancing retrieval with LLMs, while also owning the inference layer and advancing evaluation practices. Experience with production ML, multi-objective optimization, and online testing is required, with a preference for expertise in multi-task learning, causal modeling, and low-latency ranking services.

What you'd actually do

  1. Architect the ranking backbone that unifies query understanding, personalization, multi-objective ranking, ads, and merchandising into a single adaptive platform.
  2. Design and build a search autosuggest system optimized for personalization and value-based relevance.
  3. Design long-horizon objective functions (e.g., incrementality, LTV, habit formation) and build uplift/causal value models that move beyond short-term engagement.
  4. Develop production-grade Multi-Task Learning (e.g., shared encoders, MMOE/PLE task heads) to jointly learn relevance, propensity, margin, and churn risk—ensuring calibration, constraints, and explainability.
  5. Own the inference layer: goal-aware re-rankers, diversity and quality constraints, safe exploration, and millisecond-class latency optimization.

Skills

Required

  • 5+ years applying ML at scale
  • 3+ years in technical leadership
  • proven track record improving ranking or recommendation systems in production
  • Demonstrated success in applying multi-objective or constrained optimization to balance relevance, revenue, margin, and user experience
  • experience with online testing and attribution beyond CTR
  • Strong coding (Python)
  • data fluency (SQL/Pandas)
  • expertise in classic ML techniques (e.g., XGBoost)
  • deep learning frameworks (TensorFlow/PyTorch)
  • Excellent analytical skills
  • strong cross-functional communication abilities

Nice to have

  • Expertise in multi-task learning architectures (e.g., MMOE/PLE, shared encoders), calibration, counterfactual evaluation, uplift/causal modeling, and/or contextual bandits for exploration.
  • Experience building low-latency ranking services, including feature stores, caching, vector + lexical retrieval, re-ranking, and A/B testing infrastructure, with expertise in constraint-aware inference.
  • Hands-on experience with LLMs as feature/recall enhancers (e.g., embeddings, adapter tuning) while maintaining clarity on when the ranker should arbitrate.

What the JD emphasized

  • proven track record improving ranking or recommendation systems in production
  • experience with online testing and attribution beyond CTR
  • Expertise in multi-task learning architectures
  • Experience building low-latency ranking services

Other signals

  • ranking models
  • recommendation systems
  • multi-objective optimization
  • LLM-enhanced retrieval
  • value-aware optimization