Capstone: A Comment Thread API

In this lesson, we will design the client-facing API for a comment thread. The example combines pagination, local writes, retries, and live updates.

Assume the interviewer asks:

Design a mobile comment thread where users can read comments and replies, post a comment, like a comment, and see new activity.

1. Define a manageable scope

Assume two levels: parent comments and replies to those parents. Arbitrarily deep reply nesting is outside this example.

The first page returns up to 20 parent comments. Each parent may include two reply previews