Comment by nitwit005

Every company I've worked with has started with an ER diagram for their primary database (and insisted on it, in fact), only to give up when it became too complex. You quickly hit the point where no one can understand it.

You then eventually have that same pattern happen with services, where people give up on mapping the full thing out as well.

What I've done for my current team is to list the "downstream" services, what we use them for, who to contact, etc. It only goes one level deep, but it's something that someone can read quickly during an incident.