The QuarkChain consists of two layers of blockchains. We apply elastic sharding blockchains (shards) as the first layer, and a root blockchain that confirms the blocks from the shards as the second layer.
Cross-shard transactions can be issued at any time, and confirmed in minutes. The throughput of cross-shard transactions increases linearly as the number of shards increases.
We designed a game theoretic framework for incentives, where hash powers are incentivized to distribute evenly among shards. There are at least 50% of overall hash power allocated to the root chain to prevent double spending attack.