Sometimes, you want to display a stream of things as they arrive, as soon as possible after they arrive. This is usually called "real time" display (or "real time" [whatever]), and you can use this tag to denote it.
The Stack Exchange API can do sort-of reasonably well at this: most routes are cached for 60 seconds. This is fast enough for a lot of purposes, although maybe not trying to FGITW something on Stack Overflow. (It is rumored that /events is updated faster; this is currently untested.) If you need faster updates than that, the API cannot help you; this is mainly to deter API-based scrapers, or something like that.
