DatabaseIF
Versus

Postgres vs MySQL

Feature PostgreSQL MySQL (InnoDB)
Architecture Process per connection. Higher memory overhead per connection. Thread per connection. Generally lower memory footprint.
JSON Support `jsonb` is legendary. Can be indexed and queried efficiently. Has JSON data type, but historically less performant than Postgres.
Extensibility Extremely high. PostGIS for geospatial, TimescaleDB, custom types. Limited. Focus is on core relational features.
Replication Logical and physical replication. Historically harder to set up. Master-slave replication is rock solid and famously easy to configure.

The Verdict

If you are starting a new project today, default to PostgreSQL. It has superior compliance to SQL standards, better handling of complex queries, and the `jsonb` column type often negates the need for a separate NoSQL database. MySQL remains an excellent choice if you have existing expertise, need simpler replication setups, or are building read-heavy applications where connection pooling overhead must be absolutely minimized.