Liquidation's trigger mechanism revolves around the Health Factor (HF), calculated as: (Collateral Value × Liquidation Threshold) ÷ Borrow Amount. In Aave, ETH's liquidation threshold is 82.5% — deposit $10,000 ETH, borrow up to $8,000, liquidation threshold is $8,250 (exceeding this triggers liquidation). When ETH price falls, the dollar value of collateral decreases. With borrowing amount unchanged, the Health Factor falls. When Health Factor drops below 1.0, anyone (a liquidator) can step in to buy your collateral at a 5-15% discount as their incentive. This mechanism is fully decentralized — no centralized entity decides whether to liquidate you. The smart contract automatically calculates and executes based on price. This is why DeFi liquidations are faster and more unforgiving than traditional finance margin calls.
RWA tokens (OUSG, PAXG) used as DeFi lending collateral have a unique characteristic in terms of liquidation risk. OUSG's NAV rises daily as underlying Treasuries accrue interest — if you use OUSG as collateral, your collateral value increases slightly every day, meaning your effective liquidation threshold rises slightly daily as well. This property makes OUSG safer collateral than most crypto assets: your collateral isn't 'sitting static waiting to be liquidated' — it's 'actively expanding your liquidation buffer' every day. PAXG is slightly different: gold doesn't generate interest, so PAXG's NAV fluctuates with gold spot prices, which can trigger liquidation. But gold's volatility is typically far lower than ETH or BTC, and gold has no history of 30%+ drops in a few hours as crypto assets do. PAXG as collateral still carries substantially lower liquidation risk than pure crypto collateral.
A 'Liquidator' is a special role in the DeFi ecosystem — anyone can be a liquidator, provided they have sufficient capital and technical ability to act quickly. Liquidator mechanics: they continuously monitor all positions' Health Factors across lending protocols. When a position's HF drops below 1.0, they immediately call the protocol's liquidation function, buying collateral at a discount. The discount (typically 5-10%) is the liquidator's profit. This mechanism means DeFi protocols don't need to maintain their own liquidation infrastructure — the market itself has participants competing for liquidation profits, ensuring problematic positions are cleared quickly. Liquidation competition is extremely intense; large liquidators use automated MEV bots operating at millisecond speed. Individual users rarely win liquidation races. This also means once your position enters the liquidation zone, it's executed nearly instantly — no reaction time.
In the context of RWA tokenized collateral, several special liquidation risk scenarios require awareness. Oracle failure: if OUSG or PAXG's oracle returns an incorrectly low valuation (technical failure or attack), the smart contract calculates Health Factor based on this wrong value, potentially triggering liquidation that should not occur. This is a systemic risk specific to tokenized assets — the underlying asset (Treasuries, gold) is fine, but wrong price data triggers liquidation. Borrow rate spike causing indirect liquidation: DeFi borrowing rates are dynamic. If borrowing demand surges on a given chain or protocol (e.g., during market panic), borrow rates can double within hours. If your borrow rate jumps from 5% to 15%, accrued interest increases rapidly — effectively increasing your borrow amount, lowering Health Factor, potentially triggering indirect liquidation. Issuer service suspension liquidity crisis: if an RWA token issuer temporarily suspends redemptions (compliance review), secondary market liquidity can rapidly contract. Tokens may trade at discount; oracles may update to discounted market prices, further depressing Health Factor.
After the FTX collapse in November 2022, the crypto market experienced large-scale cascading liquidations over several days. In Aave's lending pool, positions with collateral exceeding $100M were liquidated within 24 hours as ETH prices rapidly fell amid panic sentiment, triggering a cascade of Health Factor declines and liquidations. Liquidated borrowers lost not just the discount on sold collateral but paid liquidation penalties exceeding 10% — meaning a previously well-collateralized position lost 10-15% of principal within hours of market panic. This case illustrates why maintaining LTV well below the liquidation threshold matters: even when your underlying thesis is correct (ETH has long-term value), short-term market sentiment can liquidate your position before you have any reaction time. Had the same position used OUSG (tokenized Treasuries) as collateral, the daily NAV increase provides additional buffer — under equivalent market pressure, liquidation is less likely to trigger.
Liquidation in DeFi lending is a necessary evil: it's the foundation that allows protocols to operate trustlessly and permissionlessly. Without liquidation, protocols need human intervention for bad loans — reverting to centralized traditional finance models. For borrowers, liquidation risk is the necessary cost of DeFi leverage, requiring active management. If you cannot or are unwilling to continuously monitor your lending positions, the best strategy is either to avoid DeFi lending entirely, or to use only RWA tokens (especially NAV-rising types like OUSG) as collateral with LTV held below 70% and sufficiently early alerts, minimizing liquidation risk. Liquidation itself has no moral dimension — it's just math. The problem is many users don't truly understand how it works until they've been liquidated.