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Openai·Machine Learning Engineer·Onsite - System Design / Architecture·Senior

Senior
Jun 2026

Summary

Interviewed for an ML Engineer role at OpenAI. One question that stood out was a system design problem around building a data mining pipeline for medical data, specifically extracting useful training data from it. Not a lot of details I can share but it was a meaty problem.

Questions Asked (1)

Q1

How would you design a system to mine high-quality training data from raw medical data?

System DesignData ModelingTechnical Trade-offs
Author's notes

This one had a lot of moving parts.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal: mining high-quality training data from raw medical data for ML models, likely for OpenAI. Then outline a pipeline that covers ingestion, cleaning, labeling, and quality control, emphasizing trade-offs between automation and human expertise. Conclude by discussing evaluation metrics and scalability.

Pro tip: Emphasize the importance of domain expertise and privacy compliance (e.g., HIPAA, GDPR) early on, and propose a hybrid human-in-the-loop approach to balance quality and cost. This shows you understand real-world constraints beyond pure ML.

1. Clarify Requirements and Constraints

Ask about the intended use case (e.g., diagnosis, drug discovery), data modalities (text, images, signals), and regulatory constraints. This ensures the design aligns with business and legal needs.

2. Data Ingestion and Preprocessing

Design a scalable pipeline to ingest raw data from various sources (EHRs, imaging, wearables) and perform preprocessing like de-identification, normalization, and standardization.

3. Quality Assessment and Filtering

Implement automated quality checks (e.g., completeness, consistency, outlier detection) and use models to score data quality. Filter out low-quality or noisy samples.

4. Labeling and Annotation

Use a combination of weak supervision, active learning, and expert human annotation to generate high-quality labels. Prioritize samples where the model is uncertain.

5. Iterative Improvement and Evaluation

Set up feedback loops to continuously monitor data quality and model performance. Use metrics like label accuracy, coverage, and downstream task performance to refine the pipeline.

Key Points to Mention

  • Data privacy and compliance (HIPAA, GDPR) with de-identification techniques
  • Handling multimodal data (text, images, time-series) and domain-specific challenges
  • Trade-offs between automation (scalability) and human expertise (quality)
  • Active learning and weak supervision to reduce labeling costs
  • Quality metrics and validation strategies (e.g., inter-annotator agreement, gold standards)
  • Scalability and infrastructure considerations (distributed processing, storage)

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.