A PostgreSQL database is required, you can spin up a PostgreSQL database with the bitnami PostgreSQL helm chart. Add the bitname repository:
helm repo add bitnami https://charts.bitnami.com/bitnami
And setup the Postgres database:
helm install druid bitnami/postgresql \
--version=11 \
--set image.repository=bitnamilegacy/postgresql \
--set volumePermissions.image.repository=bitnamilegacy/os-shell \
--set metrics.image.repository=bitnamilegacy/postgres-exporter \
--set global.security.allowInsecureImages=true \
--set auth.username=druid \
--set auth.password=druid \
--set auth.database=druid