Gatling: Rapid-Fire Consensus from Parallel Composition
2026-06-16 • Cryptography and Security
Cryptography and SecurityDistributed, Parallel, and Cluster Computing
AI summaryⓘ
The authors studied how blockchain systems agree on the order of transactions quickly. They designed Gatling, a new way to propose transactions faster than the usual limits set by network delays by running several agreement processes in parallel and combining their outputs. Gatling also handles cases when some leaders fail and offers versions that keep important safety guarantees. Their tests show Gatling works with existing protocols to reduce waiting times without extra tuning.
Consensus protocolBlockchainAtomic broadcastTransaction latencyLeader rotationHead-of-line blockingParallelismFault toleranceReplicated state machine
Authors
Giulia Scaffino, Max Resnick, Joachim Neu
Abstract
Consensus protocols form the core of blockchains and other replicated state machines, ensuring that all correct nodes process the same totally ordered log of input transactions. In fault-free executions, performance is driven by the good-case transaction latency -- the time between a transaction becoming known to all nodes and its confirmation by the consensus protocol -- which depends on both how frequently proposals are made and, once made, how quickly they are confirmed. While prior work has established tight lower bounds on confirmation latency that modern protocols already achieve, it remains open whether the inter-proposal time can be further reduced below the state-of-the-art of one network delay. We introduce Gatling, an atomic broadcast protocol that achieves arbitrarily small inter-proposal times under rotating leader schedules; in particular, smaller than the network delay. Gatling runs multiple parallel instances of a black-box atomic broadcast protocol and staggers their proposal schedules to generate proposals in faster succession than state-of-the-art protocols. A deterministic interleaving rule merges the outputs of these instances into a single global log. We analyze the effects of head-of-line blocking caused by crashed leaders, and derive Gatling's optimal number of parallel instances. We further study the impact of Gatling on predictable validity and present two variants that retain this property. Finally, our experiments confirm that Gatling can be used with off-the-shelf component protocols to achieve low latency without fine-tuning the component protocol for minimum latency.