We had a major issue with Google Cloud Platform some time between 2019-04-16T11:00:00Z and 2019-04-17T02:30:00Z, when all of our service accounts lost their access keys for an unknown reason, so our Google Compute Engine and Google Cloud Storage API requests failed, disrupting our production services.
ie. When we visited https://console.cloud.google.com/iam-admin/serviceaccounts, the entire column for "Key ID" displayed "No keys" and we had to create new keys for each service account to restore access.
Why or how could this happen and what can we do to prevent it happening again?