Not so much old school as I was new to JDK, there was no prior art anywhere in our codebase that implemented async (somehow, in 2022), and we started off with JDK 8 (I helped upgrade everything to JDK 17). I REALLY TRIED, OK!?

Even when I was building stuff in Kotlin, I couldn't figure out how to make async -- coroutines? RX? I forget already -- work, either. But that was all in the last few months before I left & moved back to the .NET stack.