Appchains are proposed solutions to the blockchain scalability problem. The Appchain Thesis proposes developing a new L1 for each protocol, connecting all of them together, to enhance the scalability of blockchain networks. The RollApps refers to app-specific rollups, a similar concept to appchains, offering modular solutions to split the Settlement, Execution, Data Availability, and Consensus layers. There are potential issues with this approach, including synchronous composability.