Stack Exchange provides a way to watch a question (i.e. receive real-time information about up- and downvotes, new answers, new comments, edits, closures and deletions) via WebSockets. You just have to connect to
qa.sockets.stackexchange.com and send the following message:
SITE_ID is ID of the site the question belongs to (for example
1 for Stack Overflow), and
QUESTION_ID is ID of the question.
I don't know if it's a bug or a feature, but you can watch multiple questions using a single WebSocket connection.
I would like to watch a large amount of questions, for example 10,000. Is this allowed?