When should you pick NoSQL over SQL for a brand new project?

hey everyone, kicking off a new project and trying to decide on the database. we're building a social media feed aggregator. lots of varied data structures, potentially huge scale, and need for flexibility. thinking about a NoSQL option like MongoDB or Cassandra. but then again, relational integrity and structured queries are still super valuable. when have you found yourselves leaning one way or the other, and what were the key factors that pushed you towards SQL or NoSQL for a new build? any specific trade-offs you regretted?