It’s possible to use a database meant for OLTP as a data warehouse, but as your data grows and the queries become more complex, operations start to slow down, ultimately resulting in deadlocks and missed data. The distinction we’re making here are tools, such as PostgreSQL that can be used as transactional databases, versus BigQuery, a data warehouse. A data warehouse tool should be optimized for analytical queries, with features such as columnar storage, that make it much faster to process common ad-hoc questions.