It was an online assessment. There were four stages to the assessment. We had to complete them one by one. First, we had to complete the first stage, and then it allowed us to complete the next stage.

The task is to implement a simplified version of an in-memory database. Plan your design according to the level specifications below:

Level 1: In-memory database should support basic operations to manipulate records, fields, and values within fields.

Level 2: In-memory database should support retrieving statistics about the frequency of updates to records.

Level 3: In-memory database should support multiple users and allow users to lock records.

Level 4: In-memory database should support undo and logout operations from users.

To move to the next level, you need to pass all the tests at this level.