I have the below cloud custodian policy.

- name: aws_rds_delete_instances
    resource: aws.rds
    filters:
      - or:
        - type: value
          key: tag:expires_on
          value: 0
          op: gt
          value_type: age
        - "tag:noncompliant_no_owner": present
        - "tag:noncompliant_no_department": present
        - "tag:noncompliant_no_team": present
        - "tag:noncompliant_expires_on": present
    actions:
    - type: delete
      skip-snapshot: false

When run, 5 standalone instances get filtered for deletion but none of them are deleted. I'm using

--cache-period 0

in the commands . Below are the logs

2026-04-20 14:02:25,804: custodian.policy:INFO policy:aws_rds_delete_instances resource:aws.rds region:us-east-2 count:5 time:1.97
2026-04-20 14:02:25,805: custodian.actions:WARNING delete implicitly filtered 0 of 5 resources key:DBClusterIdentifier on None
2026-04-20 14:02:25,809: custodian.policy:INFO policy:aws_rds_delete_instances action:delete resources:5 execution_time:0.00

What does this warning mean ?

WARNING delete implicitly filtered 0 of 5 resources key:DBClusterIdentifier on None

What to do such that the instances start getting deleted actually?

That action is intended for use with standalone instances. If you want to delete clusters, you can use the

aws.rds-cluster

resource: https://cloudcustodian.io/docs/aws/resources/rds-cluster.html#aws-rds-cluster-actions-delete

thats what I'm saying. they are standalone instances. they don't have

DBClusterIdentifier

key with them.

Gotcha, sorry misinterpreted what you were asking at first. That sounds like a regression then - would you mind opening an issue to track that? A comment on a closed PR is easy to lose.