Q: What does the status "Decision in process" after a week of submission mean?

Normally, a direct change from "With editor" to "Decision in process" implies a desk rejection. You have not mentioned whether your paper has been through any other status before this. However, since it's been only a week since submission, I doubt that the paper has been through peer review. In my opinion, this status change indicates desk rejection. Once a paper is submitted to a journal, it goes through an initial screening process, which is done by the editor. Only a paper that clears this initial screening is sent for peer review; else, it is rejected. This form of rejection (rejection without peer review) is known as desk-rejection.

Related reading:

• Does a direct 'Decision in Process' status indicate rejection?
• My manuscript's status changed from "With editor" directly to "Decision in process" and it remains so for over a month. Why?