We chose Polkadot for two main reasons:
Substrate: This is the backbone that powers Polkadot, a next generation, heterogeneous, multi-chain network. Most of the blockchains in the Polkadot ecosystem are also built on Substrate. It allows you to customize a blockchain by modifying the parameters in the runtime algorithm. This allows you to clearly define the parameters that should be within the "trustless" environment and which ones should be outside it for building a product that is market ready. Polkadex wanted to build an application specific blockchain by defining a set of parameters that makes an exchange trustless but at the same time user-friendly. It was only possible due to the modular framework that substrate is. For more details, visit www.substrate.io.
Ecosystem: An exchange is a market place where traders come together to negotiate price on the assets they hold. All market places need to be well connected to secondary markets for better price discovery and participation. There is no point in building an exchange with a handful of users or community because the adoption curve will be very slow. We found the Polkadot ecosystem to be a perfect fit for such a product because of the scaling issues we have in Ethereum. The technology that we are making use of will eventually help the industry to distribute some of the load which the primary networks are handling. Since the founders of Polkadot are also within the web3 ecosystem, that became the right fit for us not only to innovate but also to get access to a bludgeoning community that is eager to participate.