A workspace is your company. A project is a piece of work inside it that could finish. Docs are where you write and talk — a note, a spec, a question, a decision — the board is what needs doing, and the calendar is everything with a date on it.
Something you could finish. The test that settles it: whoever you would invite as a guest tells you where the project is. If you would give a client the whole of it, that is one project. If it runs forever and different people care about different parts, those parts are the projects and the thing on top is your workspace.
A guest gets a link, and the link is their way in — no account, no password, nothing to accept. They can read, reply, upload, and see the calendar. They cannot see anything marked team only, and they cannot reach any other project. Guests are free and are never counted.
If a guest link goes somewhere it should not have, invite the same person again: that issues a new link and immediately kills the old one.
A doc is a page: a title, a body, and comments underneath. It is the one thing a project is made of, and there is no separate place for a discussion, a proposal or a decision — they are all docs at different points in their life.
One person edits at a time. If somebody else has the pen you can take it, and their work is saved to the history first. Guests read and comment; the pen is the team's.
No DMs, no unread badges, no green dots, no live co-editing, no time tracking. Each of those is a decision rather than a gap — the about page explains why.
Email help@async.inc. It is a small operation, so you will get a person.