The first two systems I worked with using InterSystems technology were a PDP-11 running M11+ and a VAX 11/750 running M/VX. Too many years ago to count! 😊
Since then I've used most, if not all, InterSystems products up to IRIS and HealthShare today.
I'm Italian living in Switzerland and I work as Senior Consultant at GAIVOTA consultin SA, we provide professional services for InterSystems and other technologies.
Curiosity: apart from DC, I don't have ANY social account! 😁
If you want to store FHIR resources you need a FHIR Server, not a gateway, for more info:
Make sure your license include FHIR Server functionality.
Have you tried using the proper, official, documented and supported way to do that using Foreign Tables?
Does the memory leak happen using Foreign Tables ?
Maybe the way you are using the "FOR INTERNAL USE" classes is not proper/correct.
Why using something you are not supposed to use when there is a proper/supported way to do this?
I suggest to have a look to the Discussion The new $system.external interface and the linked .NET samples available in GitHub.