All ULC communication between the server and the UI engine is asynchronous in nature. This greatly enhances the scalability of both the ULC server as well as the UI engine. Since a single UI Engine can be simultaneously connected to multiple ULC servers, the user, while waiting for a reply from one ULC application can continue to work with another. This aspect allows ULC applications to stay responsive even in a wide area network where response times and network latency vary greatly. In contrast competing thin client environments like WinFrame and Terminal Server show distinct lags and pauses when used across a wide area network like the Internet.

Requests can optionally be batched together allowing multiple ULC requests to be sent within a single physical message send reducing the effect of network latency.