When I upgrade a cluster in Elastic Cloud, it leaves behind these indexes. They're named like apm-<Version>-onboarding-<Date> as-in apm-7.4.2-onboarding-2019.11.04.
I couldn't find anywhere what the purpose of them is, or if I can remove them. Not causing any issues of course but they're piling up!
The onboarding indexes contain a log of every [re]connection of apm-server to Elasticsearch primarily for use by the getting started guide and to aid in troubleshooting connectivity issues. Feel free to purge them aggressively.
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