Declarative is great if there is always one path to get to where you're going.
But I like to use the example of a Git repository where you've renamed and also changed some parts of a file. You commit the new state - was it a deletion and a brand new file, or a migration and modification of an existing resource? It's usually a non-issue because Git is smart, and files don't really care about their identity - but what if this was a database server and you need control over what happens when, and how things drain? Do you trust the system to choose the right path vs. "delete the database and make a new one?"
At some point you'll need imperative thinking to make sure your bases are covered, even if that is "we have a 3 phase rollout plan for different versions of the declarative config." And that's perfectly fine, in many cases. But it's important to never get into a cargo-cult level of "if it can't be done with one declarative change it shouldn't be done" - because then you'll either get stuck or light things on fire.
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Declarative is great if there is always one path to get to where you're going.
But I like to use the example of a Git repository where you've renamed and also changed some parts of a file. You commit the new state - was it a deletion and a brand new file, or a migration and modification of an existing resource? It's usually a non-issue because Git is smart, and files don't really care about their identity - but what if this was a database server and you need control over what happens when, and how things drain? Do you trust the system to choose the right path vs. "delete the database and make a new one?"
At some point you'll need imperative thinking to make sure your bases are covered, even if that is "we have a 3 phase rollout plan for different versions of the declarative config." And that's perfectly fine, in many cases. But it's important to never get into a cargo-cult level of "if it can't be done with one declarative change it shouldn't be done" - because then you'll either get stuck or light things on fire.