Anchor / UST / Terra collapse retrospective

The Anchor / UST / Terra collapse is the canonical case study in unsustainable yield, and one of the most instructive failure case studies of the entire DeFi era. The dynamics that killed Anchor are the dynamics that will kill the next unsustainable yield product, which is why spending an hour on this story produces returns that last for the rest of your time in crypto.

The basic chronology. Terra was a Layer 1 blockchain optimized for stablecoin and payments use cases. Its native stablecoin, UST, was algorithmic — backed not by reserves but by an arbitrage relationship with the network's volatile token, LUNA. The Anchor Protocol was Terra's flagship lending product, offering approximately 20% annualized yield on UST deposits. By early 2022, Anchor held roughly $14 billion of UST — the majority of UST's total circulating supply. The Anchor yield was the engine driving UST adoption: people held UST to deposit it in Anchor, the 20% yield being radically above what any other on-chain or off-chain dollar-denominated product offered.

The yield was not sustainable. Borrowers on Anchor paid roughly 10% interest on their loans. Depositors earned roughly 20%. The gap was paid out of Anchor's "yield reserve" — a pool of UST that the Terra Foundation kept topping up with new capital. The reserve was being depleted continuously because the protocol was structurally underwater. Terra and the Luna Foundation Guard injected hundreds of millions of dollars to refill the reserve through late 2021 and early 2022. The math could not work indefinitely without either reducing the yield (which would crater Anchor TVL and UST demand) or finding new external sources of capital.

The May 2022 collapse was the inevitable mathematical consequence. Several large UST withdrawals from Anchor in early May triggered selling pressure on UST. The arbitrage mechanism that was supposed to defend the peg required massive new LUNA supply to absorb the demand. As LUNA's supply expanded, its price fell. As LUNA fell, the peg defense became less effective. As the peg weakened, more holders sold. As more holders sold, more LUNA had to be minted. The death spiral was over within a week. $40 billion of value evaporated. Anchor's reserve, Anchor's TVL, UST's market cap, and LUNA's market cap all went to roughly zero.

The lessons. First: even when the protocol mechanics look novel, the underlying math has to work. The Anchor team built genuinely interesting smart contract infrastructure and a credible-looking economic system. None of it mattered because the yield could not be funded indefinitely. The novelty of the mechanism did not change the underlying balance sheet. Second: the warning signs were visible months in advance to anyone who looked. The reserve was being depleted publicly, on-chain. Terra Foundation refills were observable. The structural unsustainability was something analysts wrote about repeatedly before the collapse. Third: the cascade was foreseeable in shape if not in exact timing. Anyone who had thought through what would happen if UST started to depeg knew the answer was a death spiral. The timing was unpredictable; the shape of the failure was not.

The broader cascade matters too. Three Arrows Capital, the most prominent crypto hedge fund of the era, had significant UST exposure and went under within weeks of the collapse. Celsius and Voyager (with major exposure to 3AC) collapsed in the following months. The contagion eventually reached Genesis, BlockFi, and FTX. The Terra collapse was the proximate trigger for the broader 2022 crypto contagion that erased roughly $2 trillion of market value.

Read at least one in-depth retrospective. Several good ones exist — Coffeezilla's video work, the various Substack post-mortems, Matt Levine's running coverage. The specific source matters less than the time invested in understanding the pattern. The next unsustainable yield product will look different in its mechanics but identical in its underlying math. Recognizing the pattern is what protects you.