David Schwartz, co-founder of XRP Ledger and Ripple CTO Emeritus, proposed a two-component transaction reservation mechanism to address the risks of front-end and sandwich attacks on XRPL’s native DEXs and AMMs.
The proposal, made in response to concerns raised by the XRP-focused analytics account XRPresso.io, introduces priority execution guarantees for users willing to pay reservation fees, a measure of market integrity directly relevant as institutional flows into XRP products continue to grow.
The proposal is currently under discussion within the community and has not been formalized as a network amendment. This distinction is important: on the XRP Ledger, protocol changes require a qualified majority of validators to vote in favor before activation, meaning Schwartz’s design has weight but faces a defined governance process before hitting the mainnet.
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How the Ripple XRP ReservedTxns Mechanism Actually Works
The scheme introduces two new protocol components. The first is a ReservedTxns ledger object, which stores a target ledger sequence number and an array of up to 32 transaction identifiers.
When this specific ledger runs, all listed transactions present in the consensus set are processed first, before all other transactions, after which the object is deleted. The second component is a TxnReserve transaction type, which allows a user to claim a priority slot for one or more future transactions by submitting a reservation before the target ledger closes.
Three constraints govern the TxnReserve: reservation fees must be at least twice the standard transaction fees; the target ledger must be within 16 ledgers of the current ledger; and the actual transaction must set its LastLedgerSequence to match the reserved ledger.
These rules are not incidental, they define both the economic cost of using the system and the narrow time window in which it operates. The 16 register cap keeps reservations tightly tied to short-term execution, preventing the mechanism from being used as a general-purpose queue game tool.
DoS protection is built in through dynamic fee scaling: as reservation slots exceed 16, fees increase, reaching several multiples of the base pool near 30 slots. Schwartz also clarified that the XRPL server software would hold reserved transactions and only publish them when the previous ledger’s proposals are known, thereby compressing the pre-execution visibility window.
“This ensures that you can execute your trade before any trade formed after your trade is disclosed,” Schwartz said. “You’ll use this approach any time you want to make a trade that you want to make sure can’t be sandwiched or front-loaded.”
The Prominent XRPL-Specific Problem Schwartz Solves
XRPresso’s concern focuses on a structural feature of the XRP Ledger: pending transactions remain in a publicly visible queue before the ledger closes, giving validators and well-connected nodes an advance view of incoming transactions.
Since the canonical order of transactions on
Schwartz acknowledged the exposure but took issue with the framing. He argued that all participants have equal access to the public queue and that validators gain no structural advantage in ordering unless several conspire.
“If multiple validators conspired, or if a single validator attempted to do this, it would be very obvious to everyone exactly who was doing this,” he said, adding that no such attempt has been confirmed outside of a proof of concept.
He also pointed out a practical profitability constraint: extracting significant value requires both high liquidity (to generate interesting volume to target) and low liquidity (to move the price at a manageable cost), a combination rarely present on XRPL.
This argument has not entirely satisfied critics, but it distinguishes XRPL’s current risk profile from Ethereum’s historically active MEV environment.
The prominent debate in DeFi is not isolated to the XRP ecosystem. Binance co-founder Changpeng Zhao last year proposed a dark pool perpetual DEX using zero-knowledge cryptography to hide order data until execution, an approach that drew its own criticism from decentralization advocates who argued it recreates the information asymmetries that crypto was designed to eliminate.
XRPresso made a similar argument in response to Schwartz, saying targeted privacy for pending transaction details would be a cleaner long-term solution than a layer of booking fees, and pointing to implementations already in effect on competing chains.
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