All core business logic is written in PLSQL

I am offered to work on a project in which almost 80% of business logic is written in PostgresQL PLSQL stored procedures. Creating objects, deleting, updating variable objects and more. Including some strange pseudo-RPC for the exchange between services around, built on PostgresQL messages pg_notify ().

In my opinion, this is more than a strange decision, given that SQL DBMS were created for other purposes. But I would like to see a competent opinion about such an architecture. Please write as is, without limiting yourself in expressions. =)

Thanks!