Hi,
I currently run my own webserver running a Magento2 store.
What a nightmare that is - so I am moving to Shopify.
My new shopify store is built and just about ready to be launched.
I am starting to think about those final things that all take a bit of time to do before launching a new website (been doing this for 30+ years!).
When it comes to DNS, it is always slow to propagate, but we always want a quick new website launch! So when I have been in control of new website launches (many times) where we are moving to a new server, I have setup DNS such that the new website location points existing web traffic back to the old website (on the old server) up until the new site is ready to launch, and then a quick change on the new server DNS to point to the new website hosted on that same server launches the site. No waiting around for DNS propagation because that has already happened (to point DNS requests to the new web server).
I want to achieve the same thing when I launch the new shopify store.
I asked shopify support (chat) but either they don’t know, didn’t understand (I think they did), or won’t commit to actually answering my question for some odd reason?
After the above chat, I am aware that I cannot point to my existing webserver from shopify systems, so that’s a no go. I cannot point my domain name to shopify and have shopify point to my existing webserver until I am ready to launch my shopify store.
My thought is to put the shopify store LIVE, and go with the normal soft launch option of updating the name servers at that point, so that propagation begins, and starts moving traffic to shopify over time.
In the meantine (at the same time as the above) I think it might work to simply update my webservers DNS entry for my website to point to the shopify IP address , thus passing all traffic over to shopify immediately. So whilever DNS resolves to my existing webserver for my website, my DNS settings can tell that traffic to go to the shopify IP address instead. Eventually DNS would propogate and my webserver would not be involved any more.
As far as shopify setup, I will have told my shopify store what domain name to use as the primary domain, so it knows to push traffic requesting my domain name towards my website on shopify, right?
Is there anything that I don’t know about with shopify systems (being new to them) that would throw a spanner in the works here? Like them needing to see full propagation before responding to requests, or something else daft like that?
Anyone done something similar/same before?
Hoping that the simple solution here can and will work 
Cheers,
Rob