A lot of times I've seen questions about how this works when you have multiple nodes or a CDN, it can be quite tricky in theory if you have random IPs or several IPs.
The way certbot works at least for non-DNS challenges is that it will hit a random server that it resolves to, you have no control over which one it hits.
If certbot hits node 1 at first to tell it to create the well-known file, then checks node 2 or any other node, you will find auhorization fails.........
For some reason, perhaps you don't want to run a daemon or let Letsencrypt have access to your production server.
There is a way to use it like a normal CSR/CA setup in manual mode.
./letsencrypt-auto certonly --manual -d realtechtalk.com - www.realtechtalk.com
Eventually you will get prompted to create a certain path and file with certain data:
Create a file containing just this data:
Casdfasfadsfsad........