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Design an End-to-End ML System

Last updated: Mar 29, 2026

Quick Overview

This interview question evaluates ML product requirements, data/labeling, modeling, serving architecture, evaluation, monitoring, and trade-offs in a realistic interview setting. A strong answer for Design an End-to-End ML System states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

  • hard
  • OpenAI
  • ML System Design
  • Software Engineer

Design an End-to-End ML System

Company: OpenAI

Role: Software Engineer

Category: ML System Design

Difficulty: hard

Interview Round: Technical Screen

##### Question Design an end-to-end machine-learning system for a real-time recommendation product. Explain data collection, feature engineering, model training, online serving, monitoring, and scalability considerations.

Quick Answer: This interview question evaluates ML product requirements, data/labeling, modeling, serving architecture, evaluation, monitoring, and trade-offs in a realistic interview setting. A strong answer for Design an End-to-End ML System states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

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|Home/ML System Design/OpenAI

Design an End-to-End ML System

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OpenAI
Aug 4, 2025, 10:55 AM
hardSoftware EngineerTechnical ScreenML System Design
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0

Design an End-to-End ML System

System Design: Real-Time Recommendation ML System

Context

You are tasked with designing an end-to-end machine-learning system that serves real-time recommendations in a consumer-facing product (e.g., feed, products, videos). The system must handle high read traffic and evolving content and user behavior.

Assumptions (you may refine during the interview):

  • Traffic: ~10k QPS; p95 latency target ≤ 150 ms for recommendation API
  • Inventory: 10M items; daily new/expiring items
  • Feedback: clicks, likes, purchases; implicit and explicit signals
  • Privacy: user consent, PII minimization, right-to-erasure compliance

Requirements

Explain and justify the design for each of the following:

  1. Data collection and event pipeline
  2. Feature engineering and feature store (offline and online)
  3. Model training, labeling, and retraining strategy
  4. Online serving architecture (candidate generation, ranking, re-ranking)
  5. Monitoring, alerting, and experimentation
  6. Scalability, reliability, and cost considerations

Constraints & Assumptions

  • Preserve the scope, facts, inputs, and requested outputs from the prompt above.
  • If the prompt leaves a detail unspecified, state a reasonable assumption before relying on it.
  • Keep the answer interview-ready: concise enough to present, but concrete enough to implement or evaluate.

Clarifying Questions to Ask Guidance

  • Clarify users, core use cases, read/write patterns, scale, latency, availability, and data retention.
  • State explicit assumptions before making sizing or architecture decisions.
  • Prioritize the functional path first, then address reliability, security, observability, and rollout.

What a Strong Answer Covers Guidance

  • A scoped requirements summary with concrete non-goals and success metrics.
  • ML-specific data, model, evaluation, serving, and monitoring choices.
  • Reasoned trade-offs among simple and scalable designs, including bottlenecks and failure modes.
  • A validation, monitoring, migration, and launch plan appropriate for the risk level.

Follow-up Questions Guidance

  • What breaks first at 10x traffic or data volume?
  • How would you degrade gracefully during dependency failures?
  • What metrics and alerts would prove the design is healthy after launch?

Submit Your Answer to Earn 20XP

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