Appchain

Most apps deploy smart contracts on a shared chain and compete with everything else for block space. An appchain, or application-specific blockchain, flips that: the app runs its own network, tuned for its needs. Teams build them with frameworks such as the Cosmos SDK, Substrate for Polkadot, Avalanche's custom L1s, or rollup stacks that settle to Ethereum and other base chains.

The appeal is control. An exchange can design its own order-matching logic and fee model, a game can offer free transactions and fast blocks, and the app can capture fees and MEV that would otherwise go to another chain's validators. Several large derivatives exchanges and DeFi protocols have moved to their own chains for these reasons, and rollup-as-a-service providers have made launching one much cheaper.

An appchain must secure itself or rent security from a base layer, and a small validator set can be easier to attack or censor. Liquidity and users are split from other ecosystems, so bridges become necessary and add risk. Running a chain also brings infrastructure work that a smart contract deployment avoids.