Application schedulers in Kubernetes

We are using bare-metal to install Kubernetes in a data centre and we need a scheduler. What is the general recommendation ? My first option based on what I know is Quartz. Are there operators for managing such application schedulers ? Should the cluster be outside Kubernetes ? If so then it needs to access a Database that is outside Kubernetes and fire a job to contact Kafka. I was thinking of using Stimzi to run Kafka inside Kubernetes.

Any pointers ?