Latency

Latency refers to the time it takes for a single operation or request to complete, or to move data from one place to another.

Low latency means faster response times and a more responsive system. High latency can lead to lag and poor user experience.

Latency is an important quality attribute of IT systems, and required careful consideration in the design of distributed software especially. In high-volume systems, latency may need to be traded for higher throughput (aka. bandwidth), ie. increasing the amount of data that can be processed over a period of time. For example, to increase throughput you might [batch] requests together, process data in [parallel], or [spread load] across multiple servers. But these strategies can have the effect of increasing the time individual requests spend waiting in queues, thereby increasing latency.

In general, in distributed software design, latency is often more problematic than bandwidth, which tends to be fairly easy to solve (by adding more resources - processing or network capacity). In addition, network bandwidth capacities have increased exponentially over the years, but the inherent latency of network communications has not improved at the same rate.