The two single biggest factors in determining what sort of process you should have are a) cost to ship/deploy and b) cost of mistake. On one extreme are things

The two single biggest factors in determining what sort of process you should have are a) cost to ship/deploy and b) cost of mistake. On one extreme are things that are expensive to change and mistakes cause critical failures and on the other are things that are trivial to change and mistakes are easily mitigated.