Common Problems
Google Docs
Real-time Updates
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Understanding the Problem
📄 What is Google Docs?
Google Docs is a browser-based collaborative document editor. Users can create rich text documents and collaborate with others in real-time.
In this writeup we'll design a system that supports the core functionality of Google Docs, dipping into websockets and collaborative editing systems. We'll start with the requirements (like a real interview), then move on to complete the design following our Delivery Framework.
Functional Requirements
Core Requirements
- Users should be able to create new documents.
- Multiple users should be able to edit the same document concurrently.
- Users should be able to view each other's changes in real-time.
- Users should be able to see the cursor position and presence of other users.
Below the line (out of scope)
- Sophisticated document structure. We'll assume a simple text editor.
- Permissions and collaboration levels (e.g. who has access to a document).
- Document history and versioning.
Non-Functional Requirements
Set Up
Planning the Approach
Defining the Core Entities
Defining the API
High-Level Design
1) Users should be able to create new documents.
2) Multiple users should be able to edit the same document concurrently.
Collaborative Edits Breakdown
3) Users should be able to view each other's changes in real-time.
When the Document is Loaded
When Updates Happen
4) Users should be able to see the cursor position and presence of other users.
Potential Deep Dives
1) How do we scale to millions of websocket connections?
2) How do we keep storage under control?
Final Design
Some additional deep dives you might consider
What is Expected at Each Level?
Mid-level
Senior
Staff
References
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