HYDRA: Breaking the Global Ordering Barrier in Multi-BFT Consensus

TL;DR

HYDRA introduces a novel Multi-BFT consensus framework that removes the global ordering layer, enabling scalable, concurrent, and deterministic transaction execution across instances, significantly improving performance and robustness.

Contribution

HYDRA is the first Multi-BFT protocol to eliminate global ordering, using object-centric execution and lightweight coordination for enhanced scalability and correctness.

Findings

Outperforms state-of-the-art protocols in LAN and WAN environments.

Achieves high scalability with up to 128 replicas.

Maintains strong consistency while removing global ordering.

Abstract

Multi-Byzantine Fault Tolerant (Multi-BFT) consensus, which runs multiple BFT instances in parallel, has recently emerged as a promising approach to overcome the leader bottleneck in classical BFT protocols. However, existing designs rely on a global ordering layer to serialize blocks across instances, an intuitive yet costly mechanism that constrains scalability, amplifies failure propagation, and complicates deployment. In this paper, we challenge this conventional wisdom. We present HYDRA, the first Multi-BFT consensus framework that eliminates global ordering altogether. HYDRA introduces an object-centric execution model that partitions transactions by their accessed objects, enabling concurrent yet deterministic execution across instances. To ensure consistency, HYDRA combines lightweight lock-based coordination with a deadlock resolution mechanism, achieving both scalability and correctness. We implement HYDRA and evaluate it on up to 128 replicas in both LAN and WAN environments. Experimental results show HYDRA outperforms several state-of-the-art Multi-BFT protocols in the presence of a straggler. These results demonstrate strong consistency and high performance by removing global ordering, opening a new direction toward scalable Multi-BFT consensus design.