I will soon be in the situation of having two separate Marketo instances for the same company. This choice was preferred over workspaces and partitions because the teams work on totally separate audiences with completely different data models.
Do you have any experience with it? What are the pitfalls and issues to look for and avoid, and what limitations are there for this setup?
I'm thinking for example how to handle the CNAME and branding links, given that the starting domain should - and most likely will - be the same.
You can't share the same hostname for branding (tracking) domains. They will have to be distinct, though obvs. they can be under the same registered domain.
For the most part, unless you are systems-savvy, you also can't share the same hostname for LP domains. It's only possible if you follow a strict naming convention (not actually enforced by the system but by policy) so it's clear which underlying instance hosts the page.
So the official word should be that 4 (or more) different hostnames are required.
the scenario I'm looking at would be that the registered domain stays the same (e.g. company.com) and only the subdomains change, I have no issues with that. My only concern was that somehow the same domain "company.com" couldn't be shared by two different instances.
Do you see any other setup issues, for example for SPF/DKIM configuration (even though I know it's not as mandatory as they say for deliverability)?
Just make sure they let you upload your own DKIM keypair, since it will need to be the same in both instances (since they will be sharing the same M1 selector record).