DeFi Liquidations
Understand DeFi liquidation triggers, health factors, liquidator incentives, oracle and market dependencies, and how cascades create systemic stress.
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A DeFi liquidation is the protocol process that reduces an undercollateralised loan by selling or transferring collateral so debt can be repaid before lender losses grow.
Learning objectives
- Explain what triggers liquidation in an overcollateralised loan.
- Understand why liquidation bonuses exist.
- Analyse how oracle, congestion and market depth can turn liquidations into bad debt.
What it is
Borrowers can remain in control of collateral only while their position meets protocol collateral requirements. When a health metric crosses a threshold, third-party liquidators or protocol mechanisms can repay part of the debt and claim collateral at an incentive discount.
The liquidation bonus compensates liquidators for gas, market risk and execution effort. It also means the borrower loses more collateral than the debt amount repaid, which accelerates deleveraging.
How it works
A borrower with £15,000 of risk-adjusted collateral against £12,000 of debt may be safe at one price but liquidatable after a sharp collateral decline. The protocol’s oracle, not the borrower’s preferred market, usually determines the trigger.
Liquidators need access to capital. They may use their own funds, flash liquidity or integrated auctions, but they still need a path to sell received collateral without losing more than the bonus.
During a crash, many positions can cross thresholds together. Liquidators sell collateral into falling markets, which can depress prices further and trigger additional loans—a liquidation cascade.
Network congestion can make the process worse. High gas, delayed blocks or chain outages reduce liquidation capacity exactly when volatility is highest.
How to analyse it
Evaluate liquidation capacity relative to the size and clustering of positions that could become eligible under the same price shock.
| Check | Why it matters | What to verify |
|---|---|---|
| Liquidation clusters | Many loans can trigger at nearby prices. | Estimate debt/collateral becoming liquidatable at stress levels. |
| Oracle behaviour | Stale or manipulable prices can delay or mis-trigger liquidations. | Review source, update and fallback design. |
| Market depth | Received collateral must be sold or hedged. | Compare liquidation notional with executable liquidity. |
| Network capacity | Congestion can stop profitable bots from acting. | Stress gas and block capacity during volatility. |
A protocol with excellent average collateralisation can still be fragile if a large share of loans are clustered near one liquidation price. Distribution matters more than the aggregate ratio.
Borrowers should not rely on manually topping up after a threshold is reached; bots can liquidate within the same block or before a manual transaction confirms.
Worked example and thought exercise
A loan has £12,000 of collateral and £8,000 debt. A 25% collateral fall reduces the collateral to £9,000. If the relevant liquidation threshold is breached, a liquidator may repay £2,000 of debt and receive collateral worth more than £2,000 according to the liquidation bonus.
If many similar loans trigger simultaneously and the collateral market is thin, liquidator selling can produce slippage that turns theoretical collateral coverage into realised shortfalls.
Thought exercise: why can a wider liquidation bonus sometimes improve protocol solvency while worsening borrower outcomes?
Common mistakes and practical workflow
- Assuming liquidations occur at a single deterministic market price.
- Ignoring oracle and network dependencies.
- Looking only at aggregate collateralisation rather than liquidation clusters.
- Waiting until the health factor is almost 1 before planning to deleverage.
Practical workflow
- Know the protocol trigger, bonus and close-factor rules.
- Map the oracle price source used for liquidation.
- Estimate position clusters under stress scenarios.
- Compare liquidation size with market and network capacity.
- Maintain a borrower buffer that allows for gaps and transaction delays.
✅ Knowledge checkpoint
- Why do protocols pay liquidation bonuses?
- How can liquidation selling create a cascade?
- Why can a protocol become insolvent even with automatic liquidation rules?
- Why should borrowers act before the health factor reaches the trigger?
FAQs
❓ Who performs DeFi liquidations?
Usually independent bots, keepers or protocol mechanisms that are economically incentivised to repay debt and claim collateral.
❓ Can a liquidation happen without my approval?
Yes. Once protocol conditions are met, smart-contract rules can allow third parties to execute it.
❓ Do liquidations always prevent bad debt?
No. Price gaps, oracle failures, congestion or insufficient liquidity can leave losses.
❓ What is a close factor?
A rule that limits the amount of a borrower’s debt that can be liquidated in a particular action or state.
📋 Summary
DeFi liquidations are an automated credit-loss control, not a guarantee. Their effectiveness depends on oracle accuracy, liquidator incentives, market depth and network capacity under the same stressed conditions that create the need for liquidation.
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