Online journals publish fast. All of them are not predatory journals. For example Phytotaxa and Telopea in the field of plant taxonomy. The said two journals accept MS whose quality is good and it is published usually within 3-4 months, MS is reviewed and proofs are shown to the authors. They do not ask for page charge or so called processing fee.
However, it cannot be denied that most of the good journals take time to publish papers.
Try to find out if there is any good fast publishing online journal in the field of Physics too but if you in urgent need of a publication by any means, think otherwise.
Your question cannot be answered until you tell us your discipline, because these companies publish so many journals. But in general, the faster the review, the lower-quality the journal.
I usually expect three months between submission and reply from reviewers. After that, it is appropriate to inquire about progress.
Online journals publish fast. All of them are not predatory journals. For example Phytotaxa and Telopea in the field of plant taxonomy. The said two journals accept MS whose quality is good and it is published usually within 3-4 months, MS is reviewed and proofs are shown to the authors. They do not ask for page charge or so called processing fee.
However, it cannot be denied that most of the good journals take time to publish papers.
Try to find out if there is any good fast publishing online journal in the field of Physics too but if you in urgent need of a publication by any means, think otherwise.
In many fields you can put your preprint on arXiv first. You put your work there to be read (because of its ease of access), and publish it in a recognised journal to be counted (by administrators and evaluation committees). Well, that is a bit exaggerated: Good referees and editors can be very helpful for improving your article; this is necessarily a process which takes time and efforts.
But I think the written information exchange in a field like string theory mostly goes through the hep-th section of arXiv. In some period with people getting up early every Monday, to check if there was a new submission by Witten. So not too lose any hours of advantage.
Some journals, like the Physical Review, have "rapid communication" sections for short articles. But the whole construction is designed for the pre-internet era. I believe the noble intent of ResearchGate was/is to provide a better option.
Elsevier, Springer and other reputable publishers have a very sound process of quality evaluation which must take some time. So, you should not expect fast acceptance from these journals, instead you can focus on the high quality of your article to shorten this time. Of course, it also depends on your discipline.
if you mean review process, usually journals which publish letters are fast, but your work should have high quality (such novelty among usual conditions ). Rapid communication has this property too but it also harder than regular.