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Postmortem Tip of the Day: A root cause. You should have one.
This is an oldie, but a goodie. And since it continues to come up, it bears repeating.
A common mistake when folks write postmortems is to not focus not finding the root cause above almost all else. There is ample literature telling people to avoid this trap, yet here we are.
Writing a postmortem before determining the root cause is like deciding who the heroine is after writing the whole damned book.
Here's a handy checklist. SREs love checklists.