Minimmit: Fast Finality with Even Faster Blocks
Brendan Kobayashi Chou, Andrew Lewis-Pye, Patrick O'Grady
TL;DR
Minimmit introduces a fast finality SMR protocol that decouples view progression from transaction finality, allowing a small quorum ($2f+1$) to drive view changes while requiring a larger quorum ($n-f$) for finality under $n\geq 5f+1$. The approach eliminates the slow path and leverages optimisations such as threshold signatures and erasure coding to reduce communication and bandwidth bottlenecks. Formal proofs establish safety, liveness, and optimistic responsiveness, and extensive simulations in globally distributed topologies show approximately 23% lower view latency and 10%–11% lower end-to-end transaction latency than leading 2-round finality protocols. The results indicate significant practical gains for low-latency consensus in large-scale, geographically dispersed systems, with configurable trade-offs via block-size, coding, and dissemination strategies.
Abstract
Achieving low-latency consensus in geographically distributed systems remains a key challenge for blockchain and distributed database applications. To this end, there has been significant recent interest in State-Machine-Replication (SMR) protocols that achieve 2-round finality under the assumption that $5f+1\leq n$, where $n$ is the number of processors and $f$ bounds the number of processors that may exhibit Byzantine faults. In these protocols, instructions are organised into views, each led by a different designated leader, and 2-round finality means that a leader's proposal can be finalised after just a single round of voting, meaning two rounds overall (one round for the proposal and one for voting). We introduce Minimmit, a Byzantine-fault-tolerant SMR protocol with lower latency than previous 2-round finality approaches. Our key insight is that view progression and transaction finality can operate on different quorum thresholds without compromising safety or liveness. Experiments simulating a globally distributed network of 50 processors, uniformly assigned across ten virtual regions, show that the approach leads to a 23.1% reduction in view latency and a 10.7% reduction in transaction latency compared to the state-of-the-art.