Ask HN: Best wiki/notes app for a couple of developers to share notes?

As you're developers gollum may work well: it's backed by a git repo so you can edit locally and/or on a shared server.

Gollum is what powers GitHub wikis.

What size and what lifetime?

If you want something that is about 2-5 pages long and is only actively updated for 3 weeks then archived, Dropbox Paper works well for the 8 months my team has been using it.

Workflowy seems nice.

https://workflowy.com/demo/embed/

Mediawiki, dokuwiki, meemo