Which network constraint causes the performance of the application to decrease as the number of...

Bandwidth is the network constraint that affects the performance of an application as the number of users accessing the application increases. Bandwidth refers to the maximum rate of data transfer across a network path. If the bandwidth is insufficient to handle the increased traffic, the application performance will degrade, leading to slower response times and potential timeouts.

References:

Cisco DevNet Documentation - Network Performance

Cisco DevNet Associate Certification Guide