BlueBottle: Fast and Robust Blockchains through Subsystem Specialization

TL;DR

BlueBottle introduces a two-layer blockchain consensus architecture that achieves sub-second finality and high throughput by balancing security, latency, and decentralization through subsystem specialization.

Contribution

The paper presents BlueBottle, a novel two-layer consensus system combining a low-latency core with a guard layer for misbehavior detection and recovery, improving performance while maintaining security.

Findings

Reduces latency by 20-25% compared to Mysticeti

Enables optimistic sub-second finality at high throughput

Maintains strong safety and liveness under mild synchrony

Abstract

Blockchain consensus faces a trilemma of security, latency, and decentralization. High-throughput systems often require a reduction in decentralization or robustness against strong adversaries, while highly decentralized and secure systems tend to have lower performance. We present BlueBottle, a two-layer consensus architecture. The core layer, BB-Core, is an n=5f+1 protocol that trades some fault tolerance for a much lower finality latency with a medium-sized core validator set. Our experiments show that BB-Core reduces latency by 20-25% in comparison to Mysticeti. The guard layer, BB-Guard, provides decentralized timestamping, proactive misbehavior detection in BB-Core, and a synchronous recovery path. When it observes equivocations or liveness failures in the core -- while tolerating up to f<3n/5 faulty nodes in the primary layer -- guard validators disseminate evidence, agree on misbehaving parties for exclusion or slashing, and either restart the core protocol (for liveness violations) or select a canonical fork (for safety violations). Together, these layers enable optimistic sub-second finality at high throughput while maintaining strong safety and liveness under a mild synchrony assumption.