I'm just guessing. coding minutes website is two-tier architecture, this article tries to drop a hint ( embedding a youtube video) and also there can be multiple clients for the same server and a set of APIs makes it easier for us to access and store data in the Database. I'm ruling out third-tier architecture because I think third-tier is used for complex applications such as websites which use payment gateways, to deal with monetary terms etc. This is just a guess. Waiting for the answer.
Really learnt many things from the article. Just awesome.