Step 7: Scalability and Performance

Suppose a live discussion thread for a major sporting event receives thousands of comments and votes a minute, while the rest of the site carries on at its normal pace. That one thread creates six separate problems:

1. More requests than any one server can answer.
2. A database that cannot hold every post or serve every read on one machine.
3. Hot content, like the thread itself, read far more often than the database can serve.
4. Background work, like feed updates and notifications, that would slow every post and could flood the shared queues. 5