  Decentralized finance revolutionizes traditional financial systems by
leveraging blockchain technology to reduce trust. However, some vulnerabilities
persist, notably front-running by malicious actors who exploit transaction
information to gain financial advantage. Consensus with a fair order aims at
preventing such attacks, and in particular, the differential order fairness
property addresses this problem and connects fair ordering to the validity of
consensus. The notion is implemented by the Quick Order-Fair Atomic Broadcast
(QOF) protocol (Cachin et al., FC '22). This paper revisits the QOF protocol
and describes a modular implementation that uses a generic consensus component.
Moreover, an empirical evaluation is performed to compare the performance of
QOF to a consensus protocol without fairness. Measurements show that the
increased complexity comes at a cost, throughput decreases by at most 5%, and
latency increases by roughly 50ms, using an emulated ideal network. This paper
contributes to a comprehensive understanding of practical aspects regarding
differential order fairness with the QOF protocol and also connects this with
similar fairness-imposing protocols like Themis and Pompe.
