I am taking an introductory course on Distributed Systems, and while reading a introductory tutorial the author discusses that
5 Rails servers behind a single load balancer all connected to one database, is not an example of a Distributed System
for the reason that :
A system is distributed only if the nodes communicate with each other to coordinate their actions.
That got me thinking as to what are the real world examples which actually would fit into the definition of a Distributed System. I found a list here, and found that Electronic Banking is in fact an example, but I do not seem to figure out why. Going by my understanding the ATM machines do not communicate with each right? They would be communicating with some sort of a centralised server to communicate and coordinate their actions. So how would this qualify as an example?
Also could anyone give me a better definition of a Distributed System ?