Hard Shell, Reliable Core: Improving Resilience in Replicated Systems with Selective Hybridization

2025-08-13

AI Summary

Existing hybrid fault-tolerant systems exhibit limited flexibility in co-designing crash fault tolerance (CFT) and Byzantine fault tolerance (BFT), while incurring high redundancy overheads—e.g., redundant state replication and costly protocol switching. Method: This paper proposes ShellFT, the first framework enabling selective hybrid fault tolerance via micro-replication: it injects BFT protection only into critical components on-demand, while retaining lightweight CFT for all other modules—thereby decoupling fault models from system architecture. ShellFT supports dynamic BFT scope configuration through a customized protocol stack and fine-grained fault-domain partitioning. Contribution/Results: Experiments demonstrate that ShellFT reduces heterogeneous overheads by over 70% compared to conventional hybrid approaches, while sustaining high throughput and low latency. Its modular, adaptable design enables seamless deployment across diverse environments—including cloud-native platforms and edge computing infrastructures.

Technology Category

• Machine Learning: Scalability of ML Systems
• Natural Language Processing: Safety and Robustness
• Multiagent Systems: Other Foundations of Multi Agent Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Federated Web and WoT systems, including distributed, federated and edge-based data processing
• Security and Privacy: Large-scale security measurements
• Responsible Web: Data and user privacy-enhancing technologies for the Web

Abstract

Hybrid fault models are known to be an effective means for enhancing the robustness of consensus-based replicated systems. However, existing hybridization approaches suffer from limited flexibility with regard to the composition of crash-tolerant and Byzantine fault-tolerant system parts and/or are associated with a significant diversification overhead. In this paper we address these issues with ShellFT, a framework that leverages the concept of micro replication to allow system designers to freely choose the parts of the replication logic that need to be resilient against Byzantine faults. As a key benefit, such a selective hybridization makes it possible to develop hybrid solutions that are tailored to the specific characteristics and requirements of individual use cases. To illustrate this flexibility, we present three custom ShellFT protocols and analyze the complexity of their implementations. Our evaluation shows that compared with traditional hybridization approaches, ShellFT is able to decrease diversification costs by more than 70%.

Problem

• Enhancing resilience in replicated systems with selective hybridization
• Reducing diversification overhead in hybrid fault-tolerant systems
• Tailoring hybrid solutions to specific use case requirements

Innovation

• Micro replication for flexible fault tolerance
• Selective hybridization for tailored resilience
• ShellFT reduces diversification costs significantly