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

TL;DR

HYDRA addresses the fundamental scalability bottleneck of multi-BFT consensus by removing the global ordering layer. It introduces an object-centric execution model with per-object locking and deterministic deadlock resolution, enabling concurrent yet atomic execution of cross-instance transactions. The authors implement a Go prototype and demonstrate up to ~9× throughput improvements in WAN and notable latency reductions across LAN/WAN under straggler scenarios, while preserving safety and liveness. This work offers a new direction for scalable, deterministic multi-BFT designs, reducing coordination overhead and expanding the practical viability of parallel consensus in large-scale systems.

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.

Figures (7)

• Figure 1: Multi-BFT consensus paradigm. Global ordering is the core of ordering blocks across instances.
• Figure 2: Overview of Hydra. Hydra contains three key steps: transaction partition, transaction ordering, and transaction execution.
• Figure 3: Throughput and latency of Hydra, ISS, RCC, Mir, DQBFT, Ladon, and Orthrus in WAN.
• Figure 4: Throughput and latency of Hydra, ISS, RCC, Mir, DQBFT, Ladon, and Orthrus in LAN.
• Figure 5: Breakdown of latency in ISS, Orthrus, and Hydra.

Theorems & Definitions (12)

• Lemma 1
• proof
• Lemma 2
• proof
• Theorem 1: Safety
• proof
• Lemma 3
• proof
• Lemma 4
• proof