Scalability is the broad term used to talk about a cryptocurrency’s ability to work as intended as it experiences increased usage. The Stratis Platform has been built with scalability in mind. The two problems outlined in What is the cryptocurrency scalability problem? are congestion on a blockchain as usage increases and operational costs/cost to the network increases as the blockchain becomes larger.
The Stratis Platform addresses the first by offering sidechains. Smart contracts will be deployed to sidechains rather than to the mainchain. This will leave the mainchain free of transactions associated with smart contracts and hence alleviate the congestion they can cause.
The flexibility of the Stratis Platform helps to address the second problem. Users have options when using the Stratis Platform to build their application. For example, they can opt for a PoA consensus mechanism which significantly reduces cost to the network.