It's good for really easy changefeeds. Eg in a multiplayer game scenario you might have several people touching rows in a table. Any client can construct a query filtering on their particular subset and trivially just say .Changes() and then get a fast, reasonably-robust changefeed with an image-then-deltas type interface. It's not particularly low latency and the latency is quite variable - so if you're timing requirements are of the millisecond order, look elsewhere.