# XOX Fabric: A hybrid approach to blockchain transaction execution

## TL;DR

XOX Fabric introduces a hybrid transaction execution method that enhances performance and concurrency in permissioned blockchains, especially under contentious workloads, by reducing invalid transactions and preventing DoS attacks.

## Contribution

The paper presents XOX, a novel approach combining minimized invalid transactions and maximized concurrency in Fabric, improving throughput under contention.

## Key findings

- Handles over 3000 transactions per second in contentious workloads
- Reduces invalid transactions in Fabric blockchain
- Prevents client-induced DoS attacks

## Abstract

Performance and scalability are major concerns for blockchains: permissionless systems are typically limited by slow proof of X consensus algorithms and sequential post-order transaction execution on every node of the network. By introducing a small amount of trust in their participants, permissioned blockchain systems such as Hyperledger Fabric can benefit from more efficient consensus algorithms and make use of parallel pre-order execution on a subset of network nodes. Fabric, in particular, has been shown to handle tens of thousands of transactions per second. However, this performance is only achievable for contention-free transaction workloads. If many transactions compete for a small set of hot keys in the world state, the effective throughput drops drastically. We therefore propose XOX: a novel two-pronged transaction execution approach that both minimizes invalid transactions in the Fabric blockchain and maximizes concurrent execution. Our approach additionally prevents unintentional denial of service attacks by clients re-submitting conflicting transactions. Even under fully contentious workloads, XOX can handle more than 3000 transactions per second, all of which would be discarded by regular Fabric.