Relayer Exclusivity

What is relayer exclusivity?

Relayer exclusivity provides a single relayer with a time-limited period of exclusivity to fill a given deposit. Exclusivity is assigned at deposit time via the exclusiveRelayer and exclusivityDeadline arguments to an Across deposit, and are emitted as part of the V3FundsDeposited event. The exclusiveRelayer address has until the exclusivityDeadline timestamp on the destination chain to complete the fill with no risk of collisions. If the deposit remains unfilled on the destination chain beyond exclusivityDeadline then the fill becomes available for other relayers to complete.

Why is this helpful?

Speed-based relayer competition can lead to collisions and gas price competition amongst relayers. Many relayer implementations have reached a point of maturity where additional speed gains are difficult to unlock and increasingly encroach on origin chain finality guarantees.

Relayer exclusivity provides a means of retaining the speed gains that Across has unlocked for users whilst reducing uncertainty and risk for relayers. Relayer exclusivity also provides a method of evaluating relayer performance and in terms of speed and availability, and enables a pathway to future order flow preferencing. Relayers are therefore incentivised to do the following:

• Ensure that their implementations respect the exclusiveRelayer and exclusivityDeadline fields.

• Ensure that they react promptly when their own relayer address is specified on a new deposit.

How does relayer exclusivity work?

Relayer exclusivity is assigned by any entity that originates Across deposits. The predominant source of Across deposit attributes is the Across API. Relayers can signal their intention to opt-in to the pool of exclusive relayer candidates by submitting a Pull Request to the Exclusive Relayer Configuration repository. This repository exists as an interim system in order to fast-track the rollout of relayer exclusivity.

When selecting an exclusive relayer, the Across API applies a selection process that considers a number of inputs, including the relayers’ own configuration preferences and their balance on the destination chain. The exact implementation and criteria for exclusive relayer selection is maintained by Risk Labs and is subject to change in order to optimise user experience and minimise externalities that leak value from the system. Recent relayer performance may also be factored in as part of the selection criteria. Third parties integrating Across Settlement are free to apply their own relayer exclusivity selection logic as they see fit.

When is relayer exclusivity being rolled out?

Relayer exclusivity is being rolled out incrementally in the Across Bridge dapp on select routes in order to trial the system. Performance is being monitored by the Across team and adjustments will be made as required. Third-party integrators are expected to begin incorporating relayer exclusivity in Q4 2024.