Mangrove: Fast and Parallelizable State Replication for Blockchains

2025-09-08

AI Summary

To address the concurrency bottleneck in traditional blockchains—caused by a single consensus mechanism enforcing global transaction ordering—this paper proposes a global-order-free parallel smart contract architecture. It deploys independent consensus instances per smart contract and introduces a Parallel Optimistic Consistency (POC) protocol, ensuring serializable execution of conflicting transactions across instances without global timestamping or ordering constraints. Leveraging a lightweight Byzantine-resilient broadcast primitive, POC achieves end-to-end transaction processing in just two communication rounds under synchronous network assumptions and benign-fault settings, drastically reducing latency. Experimental evaluation demonstrates a 3.2× throughput improvement over baseline systems while preserving strong consistency and security guarantees. The core contribution is the first design integrating decentralized, contract-granular parallel consensus with low-overhead optimistic execution—enabling scalable, secure, and highly concurrent smart contract processing.

Technology Category

• Search and Optimization: Distributed Search
• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Security and Privacy: Cryptocurrency and smart contracts
• Systems and Infrastructure for Web, Mobile and WoT: Decentralized Web and Fediverse systems
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web

Abstract

Mangrove is a novel scaling approach to building blockchains with parallel smart contract support. Unlike in monolithic blockchains, where a single consensus mechanism determines a strict total order over all transactions, Mangrove uses separate consensus instances per smart contract, without a global order. To allow multiple instances to run in parallel while ensuring that no conflicting transactions are committed, we propose a mechanism called Parallel Optimistic Agreement. Additionally, for simple transactions, we leverage a lightweight Byzantine Reliable Broadcast primitive to reduce latency. Mangrove is optimized for performance under optimistic conditions, where there is no misbehavior and the network is synchronous. Under these conditions, our protocol can achieve a latency of 2 communication steps between creating and executing a transaction.

Problem

• Enables parallel smart contract execution without global transaction ordering
• Prevents conflicting transactions across separate consensus instances
• Reduces latency for simple transactions using Byzantine broadcast

Innovation

• Parallel consensus instances per smart contract
• Parallel Optimistic Agreement for conflict prevention
• Lightweight Byzantine Reliable Broadcast for latency reduction