+1, one can't know everything. Knowing the unknowns is often easy to fix, either learn them or find someone knows them. My company usually review postmortems of

+1, one can't know everything. Knowing the unknowns is often easy to fix, either learn them or find someone knows them. My company usually review postmortems of outages in production, almost all of them I have reviewed are because of a code change/config change that the author/operator had no idea about what could go wrong.