One of the last Schedulers that we will cover is the Executor Scheduler. It was created to consume a custom pool created with an Executors class from the java.util.concurrent package. An example of how that can be done looks like this:

final ExecutorService executor = Executors.newFixedThreadPool(10);
final Scheduler pooledScheduler = Schedulers.from(executor);

Then, it's just a matter of passing and using it in .subscribeOn():

.subscribeOn(pooledScheduler)

This Scheduler can be used to create bounded worker pools that can replace IO Scheduler in cases where the chance of creating lots of Observables is quite likely.