We are currently using an standard SSL certificate for a domain say example.com hosted on 300 servers. When someone request
https://example.com, one of the server serves the request.
Now, we want to upgrade our SSL certificate from Standard to one that protects multiple sub domains. Our registrar, GoDaddy, informed us that we will need to cancel the current certificate and instead a new one will be issued.
Now, once the new one is issued to us, it will take approximately 10 days for us to replace the older one on the 300 servers. In those 10 days, if our users request
https://example.com and a server that still has the old certificate serves the request, then what will be shown on the user's browser?
Will the user see an invalid certificate error?
NOTE: Just to put all the backlash at rest, the reason it takes 10 days to update over 300 servers are because my servers are deployed in private buses, trains and aircraft and they serve request via an offline hotspot. They may serve several requests without connecting to internet for days. And hence, as per our last update rate, it will take approx 10 days for me to update all of them.