For example Zendesk has a feature called Agent Collision Notification - when you edit a ticket you get a note if somebody else its editing this ticket.
What is the Infrastructure to support a feature like this? This question seems to aim at the same thing but at a much lower level.
For the system to be completely dynamic (also notifying the first viewer) and reasonable fast, probably some comet or websocket like stuff is needed. But unlike in chat systems (a prime comet example) in a Ticket system users are constantly switching pages.
What would be the program flow and the server infrastructure for a thing like this?
If you want to allow realtime collaboration then this question that also mentions Operational Transforms will be of interest to you. And there's also a question about operational transformation libraries.
What would be the program flow and the server infrastructure for a thing like this?
I work for Pusher so I can tell you one solution using our technology.
It would also be quite cool to use presence so you could see who else was viewing the page and to allow the users to discuss changes as they happen.