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

SeniorPrefer not to say
Jun 2026

Summary

ML system design round at Meta for an MLE role. One question, pretty open-ended, the kind where you can go in a dozen directions and second-guess yourself the whole time.

Questions Asked (1)

Q1

Design an ML system that recommends places to a user in a maps or local-discovery product.

System DesignTechnical Trade-offsProduct Sense & Ideation
Author's notes

The scope is huge and that's kind of the problem.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the product context and requirements, then outline the ML system architecture from data to serving, and finally discuss trade-offs and evaluation. Focus on how you would balance relevance, diversity, and business objectives while handling cold-start and scalability.

Pro tip: Emphasize the importance of defining clear offline and online metrics that align with user satisfaction and business goals, and discuss how you would iterate using A/B testing. Show awareness of the two-sided nature of recommendations (users and places) and how to handle feedback loops.

1. Clarify Requirements and Scope

Ask questions to understand the product (e.g., Maps vs. Local Discovery), user goals, scale, and constraints. Define success metrics and key challenges like cold-start, real-time updates, and privacy.

2. Data and Feature Engineering

Identify data sources: user interactions (searches, clicks, visits), place attributes (category, location, reviews), and contextual signals (time, weather). Discuss feature engineering for user, place, and context.

3. Modeling Approach

Propose a two-stage architecture: candidate generation (e.g., collaborative filtering, embedding-based retrieval) and ranking (e.g., gradient boosted trees or deep neural networks). Mention handling of cold-start via content-based methods.

4. Serving and System Design

Outline the serving pipeline: offline training, near-real-time updates, and online inference with low latency. Discuss scalability, caching, and fallback strategies.

5. Evaluation and Iteration

Define offline metrics (e.g., recall@k, NDCG) and online metrics (CTR, conversion, user retention). Describe A/B testing, counterfactual evaluation, and how to monitor for bias and feedback loops.

Key Points to Mention

  • Two-stage recommendation architecture: candidate generation and ranking
  • Handling cold-start for new users and new places using content-based and contextual features
  • Balancing relevance, diversity, and business objectives (e.g., promoting local businesses)
  • Real-time personalization and contextual signals (location, time, weather)
  • Evaluation metrics: offline (precision, recall, NDCG) and online (CTR, dwell time, retention)
  • Scalability and latency considerations for serving millions of users

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