The task of the Microservice is to convert the pdf to stardust and to return it to its sender. so no auth. Furthermore its most likely only reachable through the local network, or at least should be if you want some stranger not to be able to also make stardust from pdfs.
Monitoring: are you trying to say that its a lot esaier to pick up one logfile thant lets say 15? because they should be aggregated somewhere anyway no?
Deployment: Depending on anything you listed how do i do anything? Of course if have to define it but if you want a fancy example: k8s argocd canary deployments done. I literally set it up once.
security? Really? Please dont get this wrong but this feels to me like whataboutism but well here i go:
i implement security just the same way as i would in the monorepo. The thing/person/entity just has to look into more repositories ;)
It comes down do one sentence i think: State is not shared, state is communicated.