It's a common pattern with data to go through the lifecycle of an index, and then take a snapshot immediately prior to the index being deleted. It would be great if we could add functionality similar with this by combining parts of the SLM and ILM features in ES.

For example, if an index had a policy like:

{
  "policy": {
    "phases": {
      "delete": {
        "min_age": "15d",
        "actions": {
          "snapshot": {
            "policy": "my-slm-policy"
          },
          "delete": {}
        }
      }
    }
  }
}

ILM would wait until the index entered the delete phase, it would then wait until a snapshot from the my-slm-policy SLM policy had been taken (it would not manually kick off a snapshot, since that could potentially create scores of unwanted snapshots), and then it would delete the index.

/cc @yaronp68 as you asked me to open an issue for this.