A production instance is expected to handle a significant workload. By default, the server runs one process and can use only one CPU core for processing, because of the Python language GIL. However, a multiprocess mode is available so that concurrent requests can be handled, taking advantage of multiple cores.
The workers=N option sets the number of worker processes to use. As a guideline, you can try setting it to 1+2*P, where P is the number of processor cores. The best setting to use needs to be tuned for each case, since it depends on the server load and what other load intensive services are running on the server, such as PostgreSQL.
It is better to set workers too high for the load than too low. The minimum should be six due to the parallel connections used by most browsers, and the maximum is generally limited by the amount of RAM on the...