It was completely a joke as mentioned in the article :) It's not actually a blockchain, just a very crude linear merkle tree. The point is that pets are appended into the blockchain, and if enough blocks get appended that don't mention your pet's birth hash, your pet is "dead" like tamagotchi. You can read it in the article in detail.

It was an absurd application of "blockchain" in order to have a demo app to try to run on AWS Lambda within some hours and it worked! :)

I assume they picked something silly so that they would focus on the actual technical goal (assessing the viability of wasm on AWS) and not getting perfectionistic or bikesheddy about the application itself.

In a wild twist they become the next tech unicorn

We even created a $B business plan for PitPet, so it's just a matter of time...

https://docs.google.com/presentation/d/1l4VDbhTeiv1bnUtof3Op...