I didn’t ask a question. I love PostgreSQL for small relational stuff (where “small” is up to a few TB) and use it any time it’s appropriate. I wouldn’t classify it as a Big Data store, though.

That’s no criticism at all. I wouldn’t use Spark for a transactional DB because it’s not the best tool for the job. Same for PostgreSQL when the dataset grows far beyond what a single instance can reasonably process.