Until recently (~5 years I guess, possibly longer now) MySQL beat PostgreSQL in raw read performance and scalability - though you'd have to scale MySQL sooner.

Until recently (~5 years I guess, possibly longer now) MySQL beat PostgreSQL in raw read performance and scalability - though you'd have to scale MySQL sooner. PostgreSQL has been better than MySQL for high-write workloads (thanks to MVCC, if you tune autovacuum properly) and for more complex queries as the query planner understands the storage layer. Modern PostgreSQL has a much better story around horizontal scaling thanks to streaming replication and a lot of work from the Citus Data team. Query performance is greatly improved as well.