Notion Backend Engineer System Design Questions

In Notion's collaborative environment, allowing users to comment on different blocks adds significant value. A messaging system must be designed to enable users to create, retrieve, and delete comments efficiently.
Create a class CommentSystem with the following methods:
- __init__(self) -> None - Initializes an empty commenting system.
- add_comment(self, blockId: int, userId: int, content: str) -> None - Allows a user to add a new comment to a specific block.
- get_comments(self, blockId: int) -> List[Tuple[int, str]] - Retrieves all comments made on a specific block.
- delete_comment(self, blockId: int, commentId: int) -> bool - Deletes a specific comment from a block if it exists, returning a status of success.
- Example 1:
Input: cs = CommentSystem(); cs.add_comment(1, 1, 'Great work!'); cs.get_comments(1)
Output: [(1, 'Great work!')]
Explanation: The comment added successfully appears in the retrieval.
- Constraints:
- Block IDs and User IDs are non-negative integers; Comment contents are strings up to 500 characters.

Notion helps users manage documents and notes collaboratively, necessitating a robust version control mechanism to facilitate tracking changes made to any page. This functionality must accommodate concurrent modifications from multiple users.
Create a class VersionControl with the following methods:
- __init__(self) -> None - Initializes a new version control system.
- save(self, pageId: int, content: str) -> None - Saves the content for a given pageId. Each save increments the version number for that page.
- get_version(self, pageId: int, version: int) -> str - Returns the content saved at the specified version for the given pageId or empty string if not found.
- Example 1:
Input: vc = VersionControl(); vc.save(1, 'Initial content'); vc.save(1, 'Updated content'); vc.get_version(1, 1)
Output: 'Initial content'
Explanation: The first saved version for page 1 is retrieved successfully.
- Constraints:
- Page IDs are non-negative integers and contents are strings with length up to 1000.