Angelfish: Consensus with Optimal Throughput and Latency Across the Leader-DAG Spectrum

2025-09-19

AI Summary

Existing BFT consensus protocols face an inherent latency-throughput trade-off: leader-based designs achieve low latency under moderate load, while DAG-based protocols deliver high throughput but lack adaptive mechanisms to dynamically switch between paradigms and simultaneously optimize both metrics. This work proposes Angelfish—the first BFT protocol enabling dynamic, synergistic coordination between leader-driven and DAG-based execution. Its core innovations include a lightweight, adaptively tuned voting mechanism; a hybrid broadcast paradigm combining best-effort and reliable broadcast; and DAG-structured parallel proposal generation with dynamic node subsets for efficient validation. Experimental evaluation demonstrates that Angelfish matches the latency of state-of-the-art leader-based protocols (e.g., HotStuff) under moderate load while achieving peak throughput comparable to current SOTA systems—thereby substantially breaking the conventional latency-throughput bottleneck.

Technology Category

• Multiagent Systems: Mechanism Design
• Game Theory and Economic Paradigms: Mechanism Design
• Search and Optimization: Sampling/Simulation-based Search

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Security and Privacy: Large-scale security measurements

Abstract

To maximize performance, many modern blockchain systems rely on eventually-synchronous, Byzantine fault-tolerant (BFT) consensus protocols. Two protocol designs have emerged in this space: protocols that minimize latency using a leader that drives both data dissemination and consensus, and protocols that maximize throughput using a separate, asynchronous data dissemination layer. Recent protocols such as Partially-Synchronous Bullshark and Sailfish combine elements of both approaches by using a DAG to enable parallel data dissemination and a leader that paces DAG formation. This improves latency while achieving state-of-the-art throughput. Yet the latency of leader-based protocols is still better under moderate loads. We present Angelfish, a hybrid protocol that adapts smoothly across this design space, from leader-based to Sailfish-like DAG-based consensus. Angelfish lets a dynamically-adjusted subset of parties use best-effort broadcast to issue lightweight votes instead of reliably broadcasting costlier DAG vertices. This reduces communication, helps lagging nodes catch up, and lowers latency in practice compared to prior DAG-based protocols. Our empirical evaluation shows that Angelfish attains state-of-the-art peak throughput while matching the latency of leader-based protocols under moderate throughput, delivering the best of both worlds.

Problem

• Optimizing blockchain consensus for throughput and latency
• Adapting between leader-based and DAG-based consensus approaches
• Reducing communication costs while maintaining Byzantine fault tolerance

Innovation

• Hybrid protocol adapting leader-DAG spectrum
• Dynamic subset uses lightweight broadcast votes
• Reduces communication and latency effectively