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Meta·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say
Jun 2026

Summary

Meta SWE system design round focused on building a copyright violation detection system for uploaded images. The interviewer pushed hard on adversarial robustness and kept challenging a two-model design, which made the second half of the session pretty uncomfortable.

Questions Asked (5)

Q1

Design a system that detects whether a user-uploaded image infringes on any image in a copyrighted-image registry.

System DesignTechnical Trade-offs
Author's notes

I went with a VLM embedding pipeline into an ANN index, which felt like the obvious path.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then propose a high-level architecture that uses perceptual hashing and approximate nearest neighbor search for efficient similarity detection. Dive into trade-offs between accuracy, latency, and cost, and discuss how to handle scale and false positives.

Pro tip: Emphasize the importance of a human-in-the-loop review process for borderline cases and the need for a feedback mechanism to continuously improve the system's accuracy. This shows you understand real-world deployment challenges beyond just technical implementation.

1. Clarify Requirements

Ask questions to understand the scale (number of images, QPS), latency requirements, accuracy expectations, and what constitutes infringement (exact copy, near-duplicate, or derivative work).

2. High-Level Design

Outline the main components: image ingestion, feature extraction (e.g., perceptual hashing or embeddings), indexing and search, and decision logic. Consider using a pre-filtering step to reduce the search space.

3. Deep Dive into Key Components

Discuss the choice of hashing/embedding technique (e.g., pHash, dHash, or deep learning embeddings), the indexing structure (e.g., LSH, HNSW, FAISS), and how to handle scalability and updates to the registry.

4. Trade-offs and Optimizations

Analyze trade-offs between precision and recall, latency vs. accuracy, and cost vs. performance. Discuss techniques like cascading filters, caching, and parallel processing.

5. Address Edge Cases and Monitoring

Cover handling of false positives/negatives, adversarial attacks (e.g., image manipulation), and the need for monitoring, logging, and a feedback loop for continuous improvement.

Key Points to Mention

  • Perceptual hashing (pHash, dHash) and deep learning embeddings for image similarity
  • Approximate nearest neighbor search (e.g., FAISS, HNSW) for efficient large-scale retrieval
  • Trade-offs between precision and recall, and how to tune thresholds
  • Scalability considerations: sharding, distributed processing, and incremental updates
  • Handling adversarial cases like cropping, rotation, and color adjustments
  • Human-in-the-loop review and feedback mechanisms for continuous learning

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

Q2

How would you fine-tune the vision-language model for this copyright detection task?

Technical Trade-offsSystem Design
Author's notes

Talked through contrastive learning on copyright-positive pairs and mentioned hard-negative mining.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the task: what exactly constitutes copyright infringement (e.g., matching protected content, style, or watermarks) and what data is available. Then propose a fine-tuning strategy that balances performance, cost, and latency, such as parameter-efficient fine-tuning (LoRA) on a pre-trained VLM with a contrastive or classification head, and discuss evaluation metrics and deployment considerations.

Pro tip: Emphasize the trade-offs between full fine-tuning and parameter-efficient methods, and mention the importance of hard negative mining and data augmentation to handle the long-tail nature of copyright infringement cases.

1. Clarify the task and constraints

Ask questions to understand the definition of copyright infringement, the scale of data, latency requirements, and whether the model needs to detect exact matches or stylistic similarities.

2. Choose a fine-tuning approach

Decide between full fine-tuning, parameter-efficient fine-tuning (e.g., LoRA, adapters), or prompt tuning based on data size, compute budget, and deployment constraints.

3. Design the training objective and data pipeline

Select a suitable loss (e.g., contrastive, triplet, or classification) and curate a dataset with positive and hard negative examples, including augmentations to simulate real-world variations.

4. Evaluate and iterate

Define evaluation metrics (e.g., precision@k, recall, F1) and set up a validation loop with human-in-the-loop for ambiguous cases, iterating on model and data.

5. Optimize for deployment

Consider model compression, quantization, and serving infrastructure to meet latency and cost targets, and plan for continuous learning as new content appears.

Key Points to Mention

  • Parameter-efficient fine-tuning methods like LoRA to reduce compute and storage costs
  • Contrastive learning or triplet loss to learn fine-grained similarity between images and text
  • Hard negative mining to improve discrimination between copyrighted and non-copyrighted content
  • Data augmentation and synthetic data generation to handle rare infringement cases
  • Evaluation metrics that align with business goals, such as precision at high recall
  • Deployment considerations: latency, model size, and potential need for ensemble or cascade systems

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

Q3

What if the user uploads a collage image where only one section infringes on a copyrighted work?

System DesignTechnical Trade-offsAdaptability & Ambiguity
Author's notes

This is where I got into trouble.

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AI HintsAI Generated

Suggested Approach

Acknowledge the complexity of partial infringement detection and propose a multi-stage system that combines automated detection with human review. Focus on balancing accuracy, scalability, and user experience while discussing trade-offs between false positives and false negatives.

Pro tip: Emphasize that the system should not only detect infringement but also provide actionable feedback to users, such as highlighting the infringing region and suggesting removal or replacement, which improves transparency and reduces appeals.

1. Clarify Requirements and Constraints

Ask clarifying questions about scale, latency requirements, and the definition of infringement (e.g., fair use, transformative works). Establish whether the goal is to block uploads, flag for review, or notify users.

2. Design Detection Pipeline

Propose a pipeline that segments the collage into regions, runs each region through a copyright detection model (e.g., perceptual hashing, CNN-based similarity), and aggregates results. Consider using a two-tier approach: fast approximate matching followed by precise verification.

3. Handle Partial Infringement

Define thresholds for what constitutes infringement (e.g., percentage of image area, confidence score). Discuss how to handle borderline cases, such as human review or user appeals, and how to provide granular feedback.

4. Address Scalability and Trade-offs

Discuss trade-offs between detection accuracy and computational cost, and how to scale the system (e.g., distributed processing, caching). Consider false positive/negative impacts on user experience and legal risk.

5. Propose Mitigation and User Feedback

Outline actions after detection: block upload, flag for review, or allow with warning. Suggest user-facing features like highlighting the infringing region and offering options to edit or appeal.

Key Points to Mention

  • Image segmentation techniques to isolate regions of a collage
  • Perceptual hashing and deep learning models for copyright detection
  • Thresholds and confidence scores for partial infringement
  • Human-in-the-loop review for ambiguous cases
  • Scalability considerations: distributed processing, caching, and latency
  • User experience: transparent feedback and appeal mechanisms

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

Q4

How would your system handle adversarial text or watermarks overlaid on an image to evade detection?

Technical Trade-offsSystem Design
Author's notes

Blanked for a second.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the system's goal (e.g., content moderation, copyright detection) and the types of adversarial manipulations (watermarks, text overlays). Then propose a multi-layered defense: preprocessing to remove or normalize adversarial elements, robust model architectures, and continuous adversarial training. Emphasize trade-offs between robustness, latency, and accuracy.

Pro tip: Meta values scalable, production-ready solutions. Discuss how you would measure robustness (e.g., adversarial test suites) and iterate, and mention the importance of not overfitting to specific attacks.

1. Clarify requirements and threat model

Ask about the system's purpose, the expected adversarial techniques, and performance constraints. Define what 'evade detection' means in this context.

2. Preprocessing and normalization

Describe techniques to detect and remove watermarks or text overlays, such as inpainting, frequency-domain filtering, or OCR-based removal. Consider the risk of degrading legitimate content.

3. Robust model design

Propose using architectures that are inherently robust to local perturbations, such as vision transformers with attention, or ensemble methods. Incorporate adversarial training with generated examples.

4. Detection and mitigation strategies

Implement anomaly detection to flag potential adversarial inputs, and use multiple modalities (e.g., metadata, image forensics) to cross-validate. Consider a fallback to human review.

5. Evaluation and iteration

Set up a continuous adversarial testing pipeline with red-teaming to measure robustness. Monitor performance in production and update models regularly.

Key Points to Mention

  • Adversarial training with augmented data (watermarks, text overlays)
  • Preprocessing techniques like inpainting, filtering, and OCR
  • Robust model architectures (e.g., transformers, ensembles)
  • Multi-modal detection (combining image, text, metadata)
  • Trade-offs between robustness, latency, and false positives
  • Continuous monitoring and red-teaming for evolving threats

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

Q5

If someone takes a phone photo of a copyrighted physical print and uploads it, does your system treat that as infringement?

Adaptability & AmbiguityCross-functional Alignment
Author's notes

Scoped it back to the PM and legal team, which I think was the right move.

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AI HintsAI Generated

Suggested Approach

Acknowledge the complexity of copyright infringement detection, especially for user-generated content like phone photos of physical prints. Explain that the system likely uses a combination of automated detection (e.g., perceptual hashing, image recognition) and human review, but ultimately it's a policy and legal question. Emphasize that as an engineer, you'd collaborate with legal and policy teams to implement appropriate measures.

Pro tip: Show awareness that this is not purely a technical problem but involves policy, legal, and product considerations. Mention that you'd seek cross-functional input to balance user experience, legal compliance, and scalability.

1. Clarify the scenario

Restate the scenario to ensure understanding: a user takes a photo of a copyrighted physical print (e.g., a poster, artwork) and uploads it. This is a user-generated content (UGC) scenario.

2. Explain technical detection methods

Describe how systems like Meta's might detect potential infringement: perceptual hashing (e.g., pHash), image recognition, and matching against databases of copyrighted works. Note that phone photos introduce distortions (angle, lighting) that make exact matching hard.

3. Discuss policy and legal considerations

Highlight that whether it's infringement depends on legal factors (fair use, jurisdiction) and platform policy. Engineers implement tools but legal teams define infringement criteria.

4. Describe the system's response

Explain that the system might flag, block, or monetize such content based on policy. It could use a combination of automated flags and human review, with appeals processes.

5. Emphasize cross-functional collaboration

Conclude that as an engineer, you'd work with legal, policy, and product teams to build and refine such systems, ensuring they are effective, scalable, and fair.

Key Points to Mention

  • Perceptual hashing and image recognition technologies
  • Limitations of automated detection for distorted images
  • Role of legal and policy teams in defining infringement
  • Fair use and jurisdictional differences
  • Scalability and false positives/negatives
  • Cross-functional collaboration and user appeals

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