How to Design Google Docs

• •Clients send document editing operations to the WebSocket Server.

• •The real-time communication is handled by the WebSocket Server.

• •Documents operations are persisted in the Message Queue.

• •The File Operation Server consumes operations produced by clients and generates transformed operations using collaboration algorithms.

• •Three types of data are stored: file metadata, file content, and operations.

One of the biggest challenges is real-time conflict resolution. Common algorithms include:

• • Operational transformation (OT)
• • Differential Synchronization (DS)
• • Conflict-free replicated data type (CRDT)

Google Doc uses OT according to its Wikipedia page and CRDT is an active area of research for real-time concurrent editing.