Ripple CTO Emeritus David Schwartz has proposed a transaction reservation mechanism for the XRP Ledger after renewed fears of front-running and sandwich attacks on the network’s payments, DEX trades, and AMM swaps. The debate reignited when marketplace XRPresso claimed that validators and well-connected nodes might exploit pre-validation queue visibility to front-run regular users.
Schwartz acknowledged the theoretical possibility but argued in a series of posts that “everyone has an equal opportunity” to see pending transactions because they are public, and that a validator acting alone gains no special advantage. He said any collusion among validators would leave clear on-chain evidence, potentially leading users to remove those validators from trusted lists.
Nevertheless, he offered a proactive solution: a new ReservedTxns ledger object that would let users reserve transaction slots in a future ledger. The proposal would require a reservation fee at least twice the normal transaction fee, limit reservations to 16 ledgers ahead, and cap each reserved object at under 32 transaction IDs. Reserved transactions would execute first in the target ledger, provided they are broadcast at the right moment and fall within the consensus set. Once executed, the reservation object would be deleted to prevent reuse.
Schwartz stressed that the scheme would protect disclosed transactions from being front-run by any transaction submitted after the reservation became visible. He also addressed denial-of-service risks, noting that escalating fees as slots fill up would make mass-slot-filling attacks costly.
The front-running discussion arrived just as blockchain security firm Halborn completed a re-audit of Ripple’s XLS-66 Lending Protocol. Halborn found no critical issues and confirmed all previously reported findings had been fixed. The protocol enables fixed-term, uncollateralized loans via Single Asset Vaults. The clean audit outcome and Schwartz’s reservation idea both feed into the broader push to expand XRPL’s DeFi stack, which already includes AMM Swappable Curves, native lending, and programmable escrow tools. While the reservation scheme is not yet a formal amendment, it offers the community a clear technical path to address transaction ordering fairness as on-chain activity grows.
