An invitation to join the editorial board of a newly launched journal I am in the first months of my postdoctoral research, where I work in a highly reputed laboratory. 

Recently, I got an invitation to join the editorial board of a newly engaged journal. They invited me because of one paper I published during my PhD, which perfectly fits within the scope of the journal. Now, I am wondering whether I should accept or not. I do not know the criteria, based on which I should take my decision. Any suggestion!
There are two types of "new" journals:


A genuinely new journal
A predatory/semi-predatory spam journal


Deciding whether to join an editorial board is largely about trying to figure out which category your invitation falls into. The first step is the email itself - is it written in clear, professional language that suggests actual editors? Stop by the journal/publisher's website - does it look legitimate? Check into the publisher's other journals if they have them - do they look like actual journals, or junk journals?

The next step is looking at the existing editorial board/editors-in-chief. Are these people you recognize in your field, and would make sense as the people to be on board? Are many of the "big names" in your field conspicuously missing?

The final step, if it passes these checks, is to actually email the editor-in-chief to talk about the journal. This serves two purposes:


It's possible for a scam journal to list someone as an editor without them knowing - contacting them directly should confirm they are indeed the editor.
It lets you talk about the journal's goals, the expected workload, etc. to make an informed choice about whether or not you have time.