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

Senior

Apr 2026

Summary

Interviewed for a software engineering role at Notion and got a system design question to design Notion itself. Not much else to go on, but it's the kind of open-ended prompt that can go a hundred different directions depending on what you prioritize.

Questions Asked (1)

Design Notion. Walk through the architecture of a collaborative document and database product like Notion.

System DesignData ModelingTechnical Trade-offs

Author's notes

This is one of those prompts that sounds clean but immediately fractures into ten different problems.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale, then propose a high-level architecture that separates the block-based document model from the underlying storage and collaboration layers. Focus on how to represent flexible content as blocks, enable real-time collaboration via CRDTs or OT, and design a scalable database for queries and permissions.

Pro tip: Emphasize the trade-offs between consistency and latency in collaborative editing, and how Notion's block model enables both documents and databases with a unified abstraction. Show awareness of real-world constraints like offline support and conflict resolution.

1. Clarify Requirements and Scale

Ask about expected user scale, read/write patterns, offline support, and consistency needs. Define core features: block-based editing, real-time collaboration, databases with views, and permissions.

2. High-Level Architecture

Outline main components: client apps, API gateway, collaboration service, block storage, database service, and search. Explain how they interact and scale independently.

3. Data Model and Storage

Describe the block model: each piece of content is a block with type, properties, and children. Discuss storage options (e.g., document store for blocks, relational DB for metadata) and indexing for fast queries.

4. Real-Time Collaboration

Explain how to sync changes across clients using CRDTs or OT, handle conflicts, and ensure eventual consistency. Mention WebSockets for real-time updates and offline queueing.

5. Scalability and Trade-offs

Discuss partitioning, caching, and CDN for static assets. Address trade-offs: consistency vs. availability, latency vs. durability, and complexity of CRDTs vs. OT.

Key Points to Mention

Block-based data model: every content unit is a block with type, properties, and children, enabling flexible documents and databases.
Real-time collaboration using CRDTs (e.g., Yjs) or OT, with conflict resolution and offline support.
Storage architecture: separating block content (e.g., in a document store) from metadata and indexes (e.g., in a relational DB) for scalability.
Database views and queries: how to support filtering, sorting, and aggregations on blocks efficiently, possibly with materialized views or indexes.
Permissions and sharing: access control at block/page level, with inheritance and real-time updates.
Trade-offs: consistency vs. latency in collaboration, complexity of CRDTs vs. OT, and cost of maintaining multiple indexes.

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