AI & Technical question
How would you implement Facebook Reactions?
- Meta
- AI & Technical
- Medium
Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.
Start a mock interview on this question · Mock interview from a job description
What this question tests
Whether the candidate can reason through a technical implementation at a system design level appropriate for a PM, including data flow and quality checks.
How to approach it
- Clarify scope: a fixed set of reaction types (like, love, haha, wow, sad, angry) attached to posts and comments, replacing or extending the single like button.
- Describe the data model: each reaction is a record tied to a user, a content object, and a reaction type, replacing the boolean like field.
- Describe the client experience: a long-press or hover reveals the reaction picker, with optimistic UI update before server confirmation.
- Describe the backend needs: aggregating reaction counts at scale in near real time, and feeding reaction data into ranking and ads relevance systems.
- Define quality checks: monitoring for reaction spam or abuse, and validating that aggregate counts stay consistent under high concurrent write load.
What a strong answer includes
- Describes the data model change explicitly, from a boolean like to a typed reaction record, showing technical grounding.
- Addresses real-time aggregation at scale as the hard engineering problem, not just the UI interaction.
- Notes that reaction data feeds ranking algorithms, connecting the feature to a broader system, not just a UI addition.
Common mistakes
- Describing only the UI (long-press menu) without addressing the backend data model or scale.
- Ignoring how reaction data would be used downstream, such as in feed ranking.
Likely follow-up questions
- How would you prevent reaction count inflation from bots or spam?
- How would you roll this out without breaking existing like-based ranking signals?
More ai & technical questions
- What happens when you enter a URL in your browser?Google · AI & Technical · Easy
- Design an in-memory cache system.Meta · AI & Technical · Hard
- How would you design an experiment to evaluate a generative AI feature when outputs are non-deterministic?OpenAI · AI & Technical · Hard
- Design a RAG-based system to support content moderation at scale, specifically for identifying misinformation.Google · AI & Technical · Hard
- Describe what happens when you send a picture using a messaging app like WhatsApp or MessengerMeta · AI & Technical · Hard
- Build the payment API for a charity event.DoorDash · AI & Technical · Medium
More questions from Meta
Learn the skill behind it
Chapters of the AI PM course that teach what this question tests.
- Chapter 1: Foundations: the model and the decisions it forces on you
- Chapter 8: Evals: define good and make the number defensible
- Chapter 6: Agents and agentic architecture