How do DeFi vaults work?

What is a DeFi vault?

A DeFi vault is a smart contract with a job. You deposit an asset, the contract deploys that asset into one or more yield strategies according to rules written in its code, and it periodically harvests the rewards and reinvests them. When you withdraw, you receive your share of whatever the vault holds. The contract does the work a hands-on DeFi user would otherwise do manually: moving between protocols, claiming rewards, swapping them back into the deposit asset, and paying gas along the way.

Yearn Finance introduced the model in 2020 on Ethereum, and Beefy Finance extended it across many chains. In both, a vault is defined by a strategy contract that can be upgraded or replaced by the protocol's governance. That is useful when a strategy stops working, and it is also a trust assumption: the people who control the strategy contract control where your assets go. Reading who those people are, and what limits they operate under, is the first step in evaluating any vault.

Vaults are efficient because they pool gas costs and compounding across many depositors. They are risky for the same reason: many depositors' assets sit behind one piece of code.

How do vaults generate yield?

The yield comes from wherever the vault's strategy puts the assets. Lending vaults supply deposits to money markets such as Aave and collect the variable interest paid by borrowers. Liquidity provision vaults deposit paired assets into an exchange pool, collect trading fees, and often also collect the pool's incentive tokens, which the vault sells and reinvests. Staking vaults stake proof-of-stake tokens or hold liquid staking derivatives and compound the protocol rewards.

Some vaults run arbitrage or basis strategies, capturing the spread between spot and derivatives markets while hedging price exposure. Others layer strategies: staking a token, using the staked receipt as collateral to borrow, and deploying the borrowed funds again. Each layer adds return and adds a dependency. A vault that touches one protocol has one thing that can break. A vault that touches three has three, plus the connections between them.

How should you read a vault's advertised APY?

The advertised APY is usually a trailing figure that blends fee income with incentive token emissions. The fee portion is earned: someone paid to borrow or to trade, and the vault collected it. The emissions portion depends on the incentive program continuing and on the incentive token holding its price. When a program ends or the token falls, that part of the APY disappears, and the trailing figure takes weeks to catch up.

Before comparing a vault's APY with the yield on a managed strategy such as Abra's USDaf or BTCaf, both variable and not guaranteed, break the vault's number into those two parts. Ask what share of the trailing yield came from fees and what share from emissions, and whether the emissions are paid in a token the vault immediately sells. A vault paying 12% that is 9 points emissions is a very different proposition from one paying 6% that is all fees. The Abra methodology page explains how the yield in Abra's own strategies is sourced, so you can run the same test on both sides.

What is a vault token, and how do withdrawals work?

A vault token is the receipt you receive when you deposit. It represents your proportional share of everything the vault holds. As the vault earns yield, each token becomes redeemable for more of the underlying asset. Vault tokens are themselves transferable and can sometimes be used as collateral elsewhere, which adds composability and, with it, another layer of risk if the vault fails.

To withdraw, you send your vault tokens back to the contract, which burns them and returns your share of the underlying asset. Most vaults process this immediately, minus any withdrawal fee. Some strategies hold assets in protocols with unbonding periods or thin liquidity, so the vault may need time to unwind positions, or may return a different asset than you deposited. Check the withdrawal terms before depositing, and check them again before you need the money. A vault you cannot exit during a market drawdown is a position you do not fully control.

What are the risks of DeFi vaults?

Smart contract risk applies twice: to the vault code and to every protocol the vault deposits into. An exploit anywhere in that chain can drain the vault. Audits reduce the odds but do not remove them, and the Curve Finance incident in July 2023 showed that a flaw can sit in the compiler beneath audited code. Vaults holding Curve positions took losses.

Oracle risk is specific to strategies that borrow or liquidate. Oracles feed external prices into smart contracts. A manipulated or stale oracle can trigger liquidation at the wrong price or allow lending against inflated collateral. Mango Markets was drained in October 2022 through oracle manipulation of its own token's price.

Impermanent loss applies to any vault that provides liquidity in a volatile pair. When the two assets in the pool diverge in price, the pool rebalances against the depositor, and the vault's harvested fees may not cover the loss relative to simply holding. The APY display rarely shows this. The Abra guide to DeFi risks covers each of these in depth.

What is composability risk, and why does it matter for vaults?

Composability is DeFi's ability to plug one protocol into another. It is what lets a vault stake a token, borrow against the staked receipt and redeploy the proceeds, all in code. Composability risk is the sum of everything that can go wrong along that chain. A vault built that way is exposed to three protocols, two oracles and a liquidation engine. A problem in any one can cascade into the others, and the vault's depositors bear the whole cascade.

Withdrawal risk sits on top. If the underlying protocol has an unbonding period, or its liquidity dries up during stress, the vault may not be able to unwind positions when depositors want out. Exits queue, or the vault returns a different asset than the one deposited. The moments when you most want to leave are the moments when everyone else does too, and that is exactly when composed positions are hardest to unwind. When you evaluate a vault, count the protocols it touches and ask what happens to each of them on a bad day, not on an average one.

How do DeFi vaults compare to managed yield strategies?

A vault and a managed strategy can hold the same underlying positions. The difference is in what surrounds them. With a vault, you select the vault, you hold the vault token in your own wallet, you bear every protocol risk directly, and your recourse if something breaks is whatever the vault's governance decides. The fee is typically a performance fee coded into the contract.

With a managed strategy at a regulated adviser, a research team selects and monitors the protocols, exposure to any one is limited, and the strategy is unwound when conditions change. Your assets sit in a separately managed account at Fireblocks Trust Company, LLC with Fireblocks MPC key management, and Abra does not rehypothecate, so undeployed assets are never reused. The adviser has a fiduciary duty to you and operates under SEC rules. You receive consolidated reporting rather than a wallet address to reconcile.

The trade is control and cost against selection, monitoring, custody and accountability. Neither model removes smart contract risk. A managed strategy that deploys into a protocol that is exploited takes the loss just as a vault would. What it changes is how many bad protocols reach your portfolio and how much sits in any one of them.

Should you use a DeFi vault or a managed platform?

Choose a vault if you can evaluate strategy contracts and their governance, you are comfortable holding keys and paying gas, and you want access to strategies a regulated adviser would not run. Vaults suit investors who treat DeFi as an active pursuit and who size each position to survive a total loss. They also suit smaller allocations, where advisory minimums and fees would weigh heavily.

Choose a managed platform if you want the return sources without the operational work, if your portfolio is large enough that custody, reporting and accountability matter as much as yield, and if you prefer a fiduciary between your capital and the protocols. At that scale the reporting and custody structure are often the deciding factors rather than the stated rate.

Plenty of experienced investors do both. They keep a self-directed allocation in vaults they understand and want to follow closely, and they hold the bulk of their yield exposure in a managed structure. If you already use Yearn or Beefy, the useful exercise is to list the protocols your vaults touch and compare that list, and its concentration, against what a managed strategy would hold. The comparison is usually instructive in both directions.