  Polkadot is a network protocol launched in 2020 with the ambition of
unlocking the full potential of blockchain technologies. Its novel multi-chain
protocol allows arbitrary data to be transferred across heterogeneous
blockchains, enabling the implementation of a wide range of novel use cases.
The Polkadot architecture is based on the principles of sharding, which
promises to solve scalability and interoperability shortcomings that encumber
many existing blockchain-based systems. Lured by these impressive features,
investors immediately appreciated the Polkadot project, which is now firmly
ranked among the top 10 cryptocurrencies by capitalization (around 20 Billions
USD). However, Polkadot has not received the same level of attention from
academia that other proposals in the crypto domain have received so far, like
Bitcoin, Ethereum, and Algorand, to cite a few. Polkadot architecture is
described and discussed only in the grey literature, and very little is known
about its internals.
  In this paper, we provide the first systematic study on the Polkadot
environment, detailing its protocols, governance, and economic model. Then, we
identify several limitations -- supported by an empirical analysis of its
ledger -- that could severely affect the scalability and overall security of
the network. Finally, based on our analysis, we provide future directions to
inspire researchers to investigate further the Polkadot ecosystem and its
pitfalls in terms of performance, security, and network aspects.
