So, when's the right time to ditch SQL for NoSQL?

we've been using PostgreSQL for our main app database for a few years now, and it's been solid. but lately, as we've scaled and added new features that involve a lot of unstructured data and need fast key-value lookups, i've started thinking about NoSQL. are there clear indicators that suggest it's time to consider moving away from relational databases? what patterns or metrics have you seen that signal a shift towards NoSQL is the right move