By the end you will take any DeFi yield, walk uphill to its source, name who is paying in one of five categories inside a minute, and know which of the five can last.
Every DeFi dashboard ends the same way: a number with a percent sign, flowing at you like a stream. Twelve percent here, sixty percent there. The number is loud. The source is silent.
Act 2 built the machines, and every one of them paid you something. This lesson is the master key to all of it: every stream of yield flows downhill from a source, and insiders walk uphill until they find it.
DeFi has exactly five springs. Every yield you will ever meet, from the tamest stablecoin vault to the wildest farm, flows downhill from one of them. Sometimes from two at once.
The good news: you have already drunk from four of the five without naming them. And two of the five are not springs at all. They are water trucks, and trucks eventually leave.
Walk uphill from the oldest yields and you find a sale. Traders paid a fee to swap against your liquidity when you were the house. Borrowers paid interest for your capital in the lending lesson. Both times, someone bought a service and you were the seller.
This is the oldest spring in finance, and the cleanest answer to who is paying: a customer. It flows exactly as long as demand for the service flows, and not a day longer.
The second spring paid you in the staking lesson, where it earned the name base rate. Chains need validators, so the network prints its own token to pay for security. Real work, really paid: the guards keep the ledger honest.
But notice the currency. You are paid in the very thing you are guarding. The service is real; the paycheck rises and falls with the asset it springs from, because here the spring and the stream are the same water. It flows for as long as the chain needs guards.
The third spring is the strangest. In the derivatives lesson, vault model venues paid depositors from the losses of the traders they faced. In the perps lesson, funding flowed to you because crowded longs paid to keep their position open. You were the other side.
Uphill from this yield stands a person: someone losing, or someone paying to hold a position. The stream flows exactly as long as the other side keeps showing up. No one on the other side, no yield.
Walk uphill from the fourth stream and there is no spring. There is a truck. A protocol prints its own token and hands it to you for parking your liquidity with it. Function first: paying rent for capital with freshly printed money. The names: emissions, liquidity mining.
The money is real while the token holds its price. But every truck runs on a schedule, and every schedule ends. Insiders even coined a term for springs one through three by contrast: real yield. Prove you can define it.