We'll discuss our approaches to picking technical solutions for the systems we design. We'll consider their advantages and limitations. We'll share the facts about the changes in our engineering culture when import substitution requirements came into effect. We migrated the system with a classical three-tier architecture from Oracle to Postgres Pro DBMS. In my presentation I'll pay attention to data migration tools and peculiarities of development Java/Kotlin apps and SQL interoperability between two DBMSs.