  In the realm of e-commerce, popular platforms utilize widgets to recommend
advertisements and products to their users. However, the prevalence of mobile
device usage on these platforms introduces a unique challenge due to the
limited screen real estate available. Consequently, the positioning of relevant
widgets becomes pivotal in capturing and maintaining customer engagement. Given
the restricted screen size of mobile devices, widgets placed at the top of the
interface are more prominently displayed and thus attract greater user
attention. Conversely, widgets positioned further down the page require users
to scroll, resulting in reduced visibility and subsequent lower impression
rates. Therefore it becomes imperative to place relevant widgets on top.
However, selecting relevant widgets to display is a challenging task as the
widgets can be heterogeneous, widgets can be introduced or removed at any given
time from the platform. In this work, we model the vertical widget reordering
as a contextual multi-arm bandit problem with delayed batch feedback. The
objective is to rank the vertical widgets in a personalized manner. We present
a two-stage ranking framework that combines contextual bandits with a diversity
layer to improve the overall ranking. We demonstrate its effectiveness through
offline and online A/B results, conducted on proprietary data from Myntra, a
major fashion e-commerce platform in India.

Information Retrieval;Machine Learning