Cannot access more than a few virtual functions using SRIOV
SRIOV is a powerful technology with it's own challenges. Sometimes simple things are the solutions. Still you can always learn a little more about how it works behind the curtain!
InvalidHeaderValue on python & azure storage account access
Using python to access azure storage accounts can - during rollouts of new api versions - result in InvalidHeaderValue issues if the client library is requesting an api version that is not yet on the account.
ingress-nginx 1.12 & allow-snippet-annotations
If you need to use snippet annotations (why?) on ingress-nginx - you'll also need to adjust the annotation filtering.
multus - deadlock state on thick plugin
Using Multus CNI's 'thick plugin' in Kubernetes can cause pod startup deadlocks due to circular dependencies between pods and the Multus daemon. Switching to the daemonless 'thin plugin' mode effectively resolves this initialization issue.

kubernetes, cgroups v2 and failing health probes
Running Kubernetes on a systemd-based OS can lead to pods restarting endlessly due to health probe failures, caused by the systemd cgroup driver. Previously, this was fixed by modifying boot options, but a simpler approach is to switch the kubelet to use cgroupfs instead.
Can't delete kubernetes namespace (NamespaceDeletionDiscoveryFailure)
While trying to delete a namespace on a kubernetes cluster I learned that there is a resource type apiservice :-) This post shows how to unblock deletions due orphaned apiservice definitions.
mysql - online index creation
This post shows how easy it is to alter tables (in this example index creation) online to keep your sql database uninterrupted and clients online.
Ansible - pretty print output
Sometimes you want to print more or extensive information on ansible output (in this case a terraform plan). This can easily be realised using an stdout callback.