What is meant by input-output constraints in the context of application performance?

Input/output (I/O bottleneck) is a situation where an application's performance is limited by the speed of input/output operations, such as reading or writing data to disk, network requests, or database interactions. In such cases, the processor may be idle, waiting for these operations to complete, which reduces overall efficiency.

For example, if an application frequently accesses a slow hard drive to read large files, the waiting time for I/O operations will dominate over computation time. To improve performance, caching, asynchronous operations, or optimized data access can be used.