Marketplace challenges in A/B testing and how to address them

A/B testing in multi-sided marketplaces presents unique challenges due to the interconnectedness of buyers, sellers, and the platform, where traditional randomization can lead to "cross-group contamination" and network effects can amplify small changes. Despite these complexities, randomized tests are essential for assessing causal impact, and several strategies can mitigate typical pitfalls, such as cluster-based randomization, which groups naturally connected users to minimize contamination, switchback testing, which alternates treatment and control to capture cyclical patterns, phased rollouts that gradually increase exposure to a new feature to monitor ripple effects, and weighted randomization using multi-armed bandits to optimize promising variants while managing network effects. Ensuring consistent identity resolution and entity property management is crucial in maintaining reliable results, particularly when users have dual roles within the marketplace. These methods adhere to the principles of randomization and adapt them to accommodate the unique dynamics of marketplaces, thus enabling clearer insights into how market forces respond to new changes.