There is a lot of enterprisey crap, but there are also many decent libraries. In particular, i am pretty happy with the Java options for the things you mention

There is a lot of enterprisey crap, but there are also many decent libraries. In particular, i am pretty happy with the Java options for the things you mention - the PostgreSQL JDBC driver, JDBC itself, and HikariCP for pooling, the JDK HttpServer (no templating though, don't know if you need that here), the JDK HttpClient, Jakarta JSON with Joy as an implementation, and SimpleFlatMapper for CSV. None of them are perfect, but i am pretty happy churning out generic business service type things with them. I wish there was some way i could take a sabbatical from my job and come and try to rewrite your service in what i consider effective modern Java. I am pretty optimistic it would be competitive with Python in effort and maintainability, but i have no way to prove it!