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

SeniorPrefer not to say

Jun 2026

Summary

Meta system design round, one question about designing the email infrastructure for Facebook. Pretty open-ended and I wasn't sure how deep to go on the backend vs the product side.

Questions Asked (1)

Design Facebook's email system.

System DesignTechnical Trade-offsProduct Sense & Ideation

Author's notes

I spent the first few minutes just trying to scope it.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Start by clarifying the scope and requirements of Facebook's email system, such as whether it's for internal notifications or a full email service like Gmail. Then, outline a high-level architecture covering key components like email sending, receiving, storage, and spam filtering, and dive into trade-offs for scalability and reliability.

Pro tip: Emphasize the unique scale and integration with Facebook's existing infrastructure (e.g., using social graph for spam detection) to show product sense and technical depth. Discuss how you would handle email deliverability and reputation, which is often overlooked but critical.

1. Clarify Requirements

Ask questions to understand the scope: Is this for internal notifications, marketing emails, or a full email service? What are the scale, latency, and reliability requirements? What features are needed (e.g., attachments, search, spam filtering)?

2. High-Level Design

Outline the main components: email sending service, receiving service (if applicable), storage (mailboxes, attachments), indexing for search, spam filtering, and user interface. Sketch a diagram showing data flow.

3. Deep Dive into Key Components

Pick 2-3 critical components (e.g., storage, spam filtering, scalability) and discuss design choices, trade-offs, and technologies (e.g., distributed storage like Haystack for attachments, machine learning for spam).

4. Address Scalability and Reliability

Explain how the system handles Facebook-scale traffic: partitioning, replication, fault tolerance, and disaster recovery. Discuss trade-offs between consistency and availability.

5. Discuss Integration and Product Sense

Highlight how the email system integrates with Facebook's social graph, existing infrastructure, and user experience. Consider features like social spam detection, priority inbox, or unified messaging.

Key Points to Mention

Scalability: handling billions of emails per day with low latency using distributed systems (e.g., sharding, replication).
Storage: efficient storage of emails and attachments, possibly using object storage and metadata databases.
Spam filtering: leveraging machine learning and social signals (e.g., sender reputation, user reports) to combat spam.
Deliverability: ensuring emails reach inboxes by managing IP reputation, SPF/DKIM/DMARC, and feedback loops.
Integration: using Facebook's social graph for features like priority inbox or social spam detection.
Trade-offs: consistency vs. availability, cost vs. performance, and build vs. buy for components like spam filtering.

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