DeFi

You could have built: Pendle

Pendle (pendle.finance) enables interest rate trading on cryptoassets, and lets people farm more airdrop with less capital.

It's the crypto equivalent of STRIPS for bonds, it has almost $3 billion TVL, and you could have built it yourself.

In this article, I show how to recreate Pendle from scratch to demonstrate how it splits tokens into 

1. Principal (aka the deposit you leave in a protocol while you're earning yield)
2. Yield (what you get back beyond the principal when you withdraw)

That alone creates the ability for people to exchange their variable yields for a fixed yield, to farm more of an airdrop with less money, and more.

See how: https://www.jacobfrantz.com/posts/pendle