Before going live with your Magento 2 store, you will need to modify your A host record in your domain manager for the site domain. You can find the server IP in the portal of your site. This IP will be the A host record you will need to change in the DNS of the domain. Setting the TTL for the DNS to 5 mins will speed up the process of going live with your site.
After the DNS has been updated for the live site domain and the DNS change has propagated then you can go to the next step to make the site live.
In order to go live for your Magento 2 store, you can modify the master domain in the portal of your site which will run search-replace in the database and change the base URL.
You can also change the base URL in Magento from:
Admin > Stores > Settings > Configuration
The other method to change the base URL is from CLI:
bin/magento setup:store-config:set --base-url="http://sitedomain.com"
bin/magento setup:store-config:set --base-url-secure="https://sitedomani.com"
Next, you will need to make sure that a Let's Encrypt SSL certificate has been enabled for the live domain in the portal of your site.
You need to clear your browser cache and if you are using a CDN for the site then you should purge the CDN for the site domain once the domain has changed.
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