Deploying Statefull apps in K8s is really challenging when you have multiple replicas. Because as you said, all the replicas should aware of CRUD operations

For this, you have to deploy MongoDB as cluster and define StatefulSets. Below are the links starting point to explore more.

• https://kubedb.com/docs/0.9.0/guides/mongodb/clustering/replicaset/

• http://k8smongodb.net/

• https://kubernetes.io/blog/2017/01/running-mongodb-on-kubernetes-with-statefulsets/