Just substitute 'microservice' with 'unikernel' and you do broadly the same things. There's a prometheus library that you link with the MirageOS unikernel and it exports using that: https://github.com/mirage/prometheus

No FAQ for this sort of thing yet, but we should start assembling one sometime soon. Questions like this very welcome on the discussion forums: https://discuss.ocaml.org/t/ann-mirageos-4-0/9598 to help us get started.

There's a nice collection of unikernels over at: https://github.com/roburio/unikernels and https://github.com/tarides/unikernels for various infrastructure pieces (like https, smtp, dns, ip filters, etc) that are good to crib from for your own infrastructure.