Implement a Stateful Chatter Message Store
Company: Reddit
Role: Software Engineer
Category: Software Engineering Fundamentals
Difficulty: medium
Interview Round: Technical Screen
Overview: Design a stateful message store that appends ordered batches, saves current data, returns bounded neighborhoods, merges overlapping reads, and edits text. The exercise explores exact ID representation, index and cache consistency, immutable results, interval merging, dataset versioning, and append-only message history.