This random suffix is added for two reasons:
1. ....
....
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2. It allows Pulumi to do zero-downtime resource updates. Certain updates require replacing resources, rather than updating them in place, due to the way cloud providers work. By default, Pulumi creates replacements first, then updates existing references to them, and finally deletes the old resources. If it weren't for auto-naming, Pulumi would need to do things in a very different order: namely, it would need to delete resources first, and create new instances afterwards, which is far more impactful and leads to downtime.