Perp DEX liquidation designs: auctions, backstops and internalization
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Compares three liquidation designs by who is buyer of last resort and where bad debt goes: market auctions, insurance or backstop funds, and internalization by an internal counterparty. Each has distinct stress failure modes.
Liquidation engine design is one of the few places where a perp DEX stops being “a trading UI” and becomes a risk system.
When a position breaches maintenance margin, the venue must do two things fast:
1 ) reduce the account’s risk (close or shrink the position), and
2 ) decide who eats the loss if the account equity can’t cover it (bad debt).
There are three common liquidation designs. They differ mainly in who is the buyer of last resort.
➀ 𝗔𝘂𝗰𝘁𝗶𝗼𝗻𝘀 (𝗺𝗮𝗿𝗸𝗲𝘁-𝗯𝗮𝘀𝗲𝗱 𝗹𝗶𝗾𝘂𝗶𝗱𝗮𝘁𝗶𝗼𝗻)
The liquidated position is sold into an auction (sometimes Dutch, sometimes competitive bids). The goal is to find an external buyer at the best available price before the account goes negative.
➤ Strength: price discovery is explicit; losses are pushed to external takers who choose to participate.
➤ Weakness: during fast markets, auctions can fail or clear at poor prices (thin bids, latency, chain congestion).
➤ Where bad debt goes: ideally nowhere (auction clears above bankruptcy price), otherwise into a backstop (if one exists), otherwise it becomes system bad debt that must be socialized or absorbed.
➁ 𝗕𝗮𝗰𝗸𝘀𝘁𝗼𝗽𝘀 (𝗶𝗻𝘀𝘂𝗿𝗮𝗻𝗰𝗲 / 𝗿𝗲𝘀𝗲𝗿𝘃𝗲 / 𝗹𝗶𝗾𝘂𝗶𝗱𝗮𝘁𝗶𝗼𝗻 𝗳𝘂𝗻𝗱𝘀)
A venue maintains a pool designed to absorb losses when liquidations don’t clear cleanly. This can be an insurance fund (fed by fees), a dedicated backstop liquidity provider, or a hedging/market-making mandate.
➤ Strength: improves survivability in stress; makes the system less dependent on perfect market liquidity at every moment.
➤ Weakness: it’s finite. If the backstop is undersized vs tail events, it delays loss allocation (not eliminates).
➤ Where bad debt goes: first into the backstop fund, if depleted, into socialized loss mechanisms (e.g., ADL or clawbacks), depending on venue rules.
➂ 𝗜𝗻𝘁𝗲𝗿𝗻𝗮𝗹𝗶𝘇𝗮𝘁𝗶𝗼𝗻 (𝗹𝗶𝗾𝘂𝗶𝗱𝗮𝘁𝗼𝗿 𝘁𝗮𝗸𝗲𝘀 𝘁𝗵𝗲 𝗼𝘁𝗵𝗲𝗿 𝘀𝗶𝗱𝗲 𝗶𝗻𝘀𝗶𝗱𝗲 𝘁𝗵𝗲 𝘀𝘆𝘀𝘁𝗲𝗺)
Instead of auctioning externally, the system internalizes the liquidation: a designated internal counterparty (MM program, internal liquidity pool, or protocol module) absorbs the position immediately, then unwinds it over time.
➤ Strength: fastest response; less reliance on external bidders; can reduce liquidation cascades if the internal counterparty is well-capitalized.
➤ Weakness: concentrates risk. You’re trusting that the internal absorber is solvent and correctly managed.
➤ Where bad debt goes: into the internal absorber’s inventory PnL, and if that absorber can’t cover losses, it becomes a backstop failure (socialization).
“Liquidation” is not just “closing a trader.” It is the system’s method of assigning losses when reality moves faster than collateral. The best designs make that assignment explicit, fast, and predictable under stress.
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