PostgreSQL (with extensions)

PostgreSQL is the world's most advanced open-source relational database. While it is primarily an OLTP system, its extensibility makes it a surprisingly capable query engine for analytical workloads, especially when combined with extensions like Citus (for distributed processing) or columnar storage plugins. PostgreSQL is the gold standard for reliability and SQL compliance. For smaller to medium-sized analytical workloads, or when data is already stored in Postgres, it is often the most practical choice.

Its massive ecosystem and mature feature set make it an indispensable tool in any data stack.