  The emergence of blockchain technology has fostered the development of
numerous decentralized applications (dapps) in recent years Pub/sub
(publish/subscribe) systems play a crucial role by associating messages with
specific topics and propagating them from publishers to subscribers across the
network. Decentralized pub/sub aims to provide this functionality without
relying on centralized control or global network state information, enabling
message propagation among nodes in a coordinated manner. Efficiency in pub/sub
services entails ensuring that subscribers receive published messages promptly.
We introduce Topiary, a rapid and scalable protocol designed for decentralized
applications' pub/sub systems. Topiary autonomously learns an efficient
peer-to-peer (p2p) topology tailored to the publish/subscribe network. It does
so by analyzing peers' interactions with their neighbors. Inspired by concepts
from the multi-armed bandit problem, Topiary strikes an optimal balance between
maintaining connections with well-connected neighbors and exploring new
connections within the network, based on their topical needs. Through
experimental evaluations, Topiary has shown a 50% reduction in broadcast
latency while achieving an interested topic coverage of over 98%, marking it as
a promising solution for efficient decentralized pub/sub networks.
