maximumPoolSize endpoint option of the Netty component is effectively ignored. We keep OrderedMemoryAwareThreadPoolExecutor in the NettyComponent#executorService field - it means that we keep, configure and start the executor on the component, not the endpoint level.
Netty component is started before the endpoint is created, so NettyComponent#executorService will be always created with the default size (before endpoint will set the pool size on the configuration object).
There is a workaround for this issue (changing configuration on the component level), but if we provide maximumPoolSize on the endpoint, then we should respect it.
IMHO it is impossible to configure maximumPoolSize at the endpoint level and cache executor instance in the component at the same time. Maybe we should just remove that option from the documentation of the endpoint options as maximumPoolSize should be configured only on the component level?