What to work through
Work through live comments as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- See other people's comments appear as they are posted, without a refresh
- Post a comment and see it at once
- Scroll back through older comments
- Keep up when a stream gets more comments than anyone can read
Constraints to discuss
- A comment reaches other viewers within 200 milliseconds
- The list keeps up with thousands of new comments a second on a busy stream
- A dropped connection catches up without gaps or repeats
- Reading older comments is never interrupted by new ones arriving
Need a starting point?
Watch for these common gaps as you prepare:
- Checking for new comments again and again on a fixed clock
- Redrawing the list for every single comment
- Pulling the list to the bottom while someone reads
- Showing a person's own comment twice
- Losing the comments posted during a dropped connection
Why this question is in the collection
These sources connect the problem to company interview reports or preparation guides. They do not guarantee what a company will ask you.