Designs algorithmically efficient ML systems for large-scale data processing. Applies approximate algorithms (LSH, HyperLogLog) for scalable solutions. Evaluates computational complexity of models when choosing architectures.
Roles · Data Scientist · Senior
What a Senior } should know
31 core skills, 78 in total. Expectations per skill, and what changes at the next level.
This page lists what a Senior } is expected to know and do, skill by skill. Core skills are the ones a manager and peers assess in a review cycle; the rest count only in self-assessment. Main areas: Programming Fundamentals, Backend Development, Database Management.
Core skills for a Senior
Grouped by area. The label on the right is the expected depth: Awareness, Working, Advanced or Expert.
Programming Fundamentals · 4
Designs code quality standards for ML research codebases: experiment tracking conventions, notebook-to-module refactoring patterns, reproducibility requirements. Refactors prototype models into production-grade code with proper testing. Establishes review practices balancing research speed with code maintainability.
Designs custom data structures for specific ML tasks: efficient feature stores, approximate data structures for streaming data. Optimizes data operations through memory-mapped files and zero-copy operations. Applies tries and suffix arrays for text mining.
Applies OOP/SOLID in ML system architecture: abstract model interfaces for experiment framework, strategy pattern for hyperparameter optimization, clean abstractions for data loading/transformation. Designs reusable ML experiment frameworks that allow comparing different model architectures consistently.
Backend Development · 1
Designs solutions with Python Web Frameworks for production systems. Optimizes performance and scalability. Chooses between alternative approaches. Mentors the team.
Database Management · 4
Architects end-to-end ML feature pipelines on ClickHouse, optimizing data extraction for training and inference workloads. Leverages ClickHouse's native ML functions and statistical aggregates for in-database feature computation at petabyte scale. Designs efficient data access patterns that minimize memory overhead when feeding large datasets into distributed training frameworks via chunked iteration.
Designs indexing architecture for ML data infrastructure: vector indexes (HNSW, IVF) for embedding similarity search, time-series indexes for temporal feature stores, and specialized indexes for graph-based feature engineering. Configures database indexes for efficient model serving and real-time feature retrieval. Optimizes data access patterns across training and inference pipelines.
Designs PostgreSQL architecture for ML data infrastructure: optimizes database for large-scale feature store operations, implements efficient data versioning and lineage tracking, configures partitioning and archival for training data lifecycle. Mentors team on SQL-based feature engineering patterns and data pipeline optimization.
Designs query architecture for ML data infrastructure: feature store query optimization, distributed query patterns for large-scale training data extraction, and real-time feature retrieval for model serving. Implements query caching for feature computation and automated query performance benchmarking. Mentors team on efficient data access patterns for ML workflows.
API & Integration · 1
Designs API architecture for ML services: model serving API patterns with versioning, feature store API design, experiment management endpoints. Defines API contracts for ML platform components. Mentors team on designing production-grade ML prediction APIs.
Cloud & Infrastructure · 2
Designs AWS infrastructure solutions for production data science platforms — SageMaker Pipelines for ML workflows, EMR for distributed feature engineering, and managed experiment tracking. Optimizes cost through SageMaker Savings Plans, spot training instances, and intelligent data lifecycle management. Implements security hardening with data encryption, cross-account isolation, and reproducible experiment environments.
Designs Docker infrastructure for ML workflows: reproducible training environments with pinned dependencies, GPU container orchestration for experiment pipelines, containerized model serving architecture. Implements best practices for experiment environment versioning and data volume management.
Testing & QA · 1
Designs testing strategy for ML research code: test pyramid balancing prototype speed and production reliability, statistical assertion frameworks for model quality, reproducibility testing with fixed seeds and data snapshots. Mentors team on transitioning research code to tested production modules.
Data Engineering · 5
Designs Spark-based analytical frameworks: custom MLlib transformers for domain-specific features, distributed experiment pipelines, and Spark integration with GPU-accelerated training (Rapids). Optimizes end-to-end ML workflows from data preparation to model serving at petabyte scale.
Designs end-to-end ML observability dashboards covering model lifecycle from training to production. Optimizes visualization systems for large-scale experiment tracking across teams. Implements governance frameworks for feature importance reporting and model performance transparency.
Designs data architecture with Data Quality tools. Optimizes for big data. Implements data governance and quality frameworks.
Designs ML data architecture with Pandas/Polars: feature store integration, automated feature validation pipelines, and efficient data loading for distributed training. Implements data quality frameworks for training data integrity. Creates organization-wide feature engineering libraries and standards. Mentors team on scalable data processing patterns for ML.
Architects ETL workflows for end-to-end ML pipelines including feature stores. Designs scalable feature engineering transforms, implements data versioning strategies, and builds automated training data validation gates within ETL orchestration.
Machine Learning & AI · 12
Has deep expertise extending scikit-learn with custom estimators, meta-learners and stacking ensembles for production ML. Designs model selection with Bayesian optimization and automated feature engineering. Mentors the team on experiment reproducibility and model versioning.
Architects scalable experiment tracking infrastructure: optimizes MLflow/Neptune deployments for high-throughput training, designs custom metric visualizations for complex model comparisons, and establishes governance policies for experiment metadata and artifact retention
Designs feature store architecture enabling cross-team feature sharing and discovery. Defines feature governance policies including versioning, deprecation, and access control. Mentors teams on feature engineering best practices and scalable feature pipelines.
Designs gradient boosting systems for production: incremental learning, model compression, ONNX export. Optimizes inference speed through tree pruning and quantization. Implements multi-output boosting and custom objective functions for specific business tasks.
Designs advanced RAG architectures with hybrid retrieval, re-ranking, and context window optimization for domain-critical applications. Develops custom NER and relation extraction pipelines combining LLMs with structured knowledge graphs. Mentors team on embedding space analysis and LLM evaluation methodology.
Designs scalable ML pipelines for enterprise: Kubeflow, Vertex AI Pipelines, SageMaker Pipelines. Implements continuous training, automated model promotion. Optimizes pipeline performance through caching, parallel execution, and incremental processing.
Designs MLflow tracking architectures for production ML, integrating with CI/CD and automated validation gates. Implements custom plugins for domain-specific metrics and artifact stores (S3, GCS). Establishes model registry governance with approval workflows and rollback procedures.
Designs end-to-end model monitoring architectures for production ML systems. Implements advanced drift detection combining statistical tests, model performance proxies, and business KPI correlation. Builds automated feedback loops from monitoring signals to retraining pipelines. Mentors team on observability best practices and incident response.
Designs model serving architecture: scalable inference platforms, model registry integration with automated deployment, and online/offline feature consistency guarantees. Implements advanced monitoring: data drift detection, model performance degradation alerts, and automated retraining triggers. Creates serving best practices and model deployment standards. Mentors team on MLOps patterns.
Architects complex PyTorch training with distributed data parallelism. Implements custom autograd functions for research. Leads architecture decisions: attention mechanisms, residual connections, normalization. Mentors team on PyTorch debugging and profiling with torch.profiler.
Has deep expertise in Recommender Systems Fundamentals. Designs solutions for production systems. Optimizes and scales. Mentors the team.
Designs end-to-end NLP systems with Transformer models for production: custom architectures, distributed training, model distillation and quantization. Optimizes inference latency and throughput for real-time applications. Mentors team on advanced techniques like multi-task learning and domain adaptation.
Version Control & Collaboration · 1
Designs code review processes for ML research: experiment code review standards, model training reproducibility checklists, research-to-production transition review gates. Mentors team on balancing research freedom with production code quality in reviews.
Additional skills
Not assessed by the team, but part of the self-assessment and the development plan.
What changes at Lead
77 skills get a higher expectation or become core when moving from Senior to Lead. The biggest jumps first.
- Algorithms & Complexity: Advanced → Expert
- Apache Spark: Advanced → Expert
- AWS: Advanced → Expert
- BI Dashboards: Advanced → Expert
- Classical ML (scikit-learn): Advanced → Expert
- ClickHouse: Advanced → Expert
- Code Quality & Refactoring: Advanced → Expert
- Code Review: Advanced → Expert
- Data Quality: Advanced → Expert
- Data Structures: Advanced → Expert
} in the open competency matrix: 78 skills across 5 levels. The matrix is free for individuals and stays free.