Blockchain is a good way to order block of sequential data that can be validated by others. Countless real-world examples show that it scales pretty well.
In my app, I am testing the use of a blockchain for storing "chat app data" selfhosted-only. The app is a work-in-progress proof-of-concept and experimental. It is an investigation into creating a distributed and decentralized app.
Unlike traditional blockchains, the sole purpose of this blockchain is to keep messages between peers in sync. The implementation is have is far from finished, but i have a testable proof-of-concept. The blockchain is entirely in javascript running in a browser.