Newer linux have replaced mcelog with edac-util. I think most shops operating systems at that scale are getting their ECC errors out of band with IPMI SEL, though.
It's rasdaemon these days: https://www.setphaserstostun.org/posts/monitoring-ecc-memory...
Looks like `mcelog --client` might be a starting place? Feed that into your metrics pipeline and alert on it like anything else...