Moving from MySQL to PostgreSQL looks easy at first.
The SQL fundamentals are still there. SELECT, JOIN, GROUP BY, CTEs, window functions, indexes, and transactions all feel familiar.
Then the small differences start causing problems.
PostgreSQL is stricter about types, folds unquoted identifiers to lowercase, uses different syntax for upserts, handles NULL ordering differently, and gives you features such as JSONB, native arrays, partial indexes, expression indexes, and transactional DDL.
Some of these differences produce immediate errors. Others are more subtle.
For example, a MySQL application that relies on case-insensitive LIKE searches can return fewer results after moving to PostgreSQL without throwing an obvious error. MySQL-specific patterns such as AUTO_INCREMENT, INSERT IGNORE, REPLACE INTO, LIMIT 10, 20, and ON DUPLICATE KEY UPDATE also need different PostgreSQL equivalents.
Then there is the operational side.
PostgreSQL's MVCC implementation, autovacuum, dead tuples, connection costs, transactional DDL, and pooling introduce concepts that MySQL developers need to understand before running a production workload.
The article also covers JSONB and GIN indexes, partial and expression indexes, CREATE INDEX CONCURRENTLY, RLS, common data type mappings, and the practical question of when PostgreSQL or MySQL makes more sense.
I break down the differences with real SQL examples and a quick-reference cheat sheet here:
https://devencyclopedia.com/blog/postgresql-for-mysql-developers
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