Postgres for almost anything. Robustness, ecosystem, accuracy, all top notch.

One exception: I did migrate two very large tables (15B+ rows) from Postgres to MySQL for performance reasons. InnodB (MySQL storage engine) can arrange the records on page by primary key, and if you have a multi-value PK (user_id, uuid) it means all records from a user are in the same set of pages. Huuuuge improvement over having your data for a user spread out over N different pages. Memory cache way more efficient. Orders of magnitude speed up on cold queries, better cache hit rate, and cost reduction from smaller servers.