I was hoping there might be an option to preserve the ids. I understand that the PUT option will create the resource and preserves ids even if the resource didn't exist already. When I attempt that via the Bundle, the system responds with, "404"

Good question @brian0098 ! This is not something we support at this time, but it is on our roadmap to support by Q2 of this year. The feature is called "Client Assigned IDs", and we have full writeup of how we would implement it, and it's implications https://github.com/medplum/medplum/discussions/1175

Thanks. Looks like it is on the right track

I'm glad you think so! We'll keep you posted as we make progress

> Much easier to support FHIR server mirroring (i.e., system-to-system synchronization) This is the big win for us.

Yeah, this seems to be the driving use case. Would love to learn more about what kinds of systems you're mirroring?