Plasma focuses exclusively on execution because modular blockchain design recognizes that different functions have fundamentally different requirements and attempting to handle everything creates unavoidable compromises. By specializing in execution, Plasma can optimize entirely for computational throughput and low latency without being constrained by the security and finality requirements that settlement demands.
Settlement requires strong security guarantees, global consensus, and irreversibility that naturally limit throughput. Ethereum as a settlement layer prioritizes these properties because reversed or disputed settlements would undermine trust in the entire system. Execution, however, benefits from speed and flexibility where transactions can be processed optimistically and batched efficiently. Plasma recognizes this distinction and pushes execution off the settlement layer entirely, processing transactions in an environment optimized for performance rather than security finality.
This separation allows Plasma to achieve dramatically higher transaction volumes by running execution in a less constrained environment while inheriting settlement security from Ethereum. The execution layer can experiment with different virtual machines, consensus mechanisms, or optimization strategies without affecting the settlement layer's stability. When execution and settlement are coupled on a single chain, innovations or changes risk destabilizing the entire system, but modularity allows each layer to evolve independently.
The focus on execution also clarifies the security model and makes it easier to reason about trust assumptions. Users understand that Plasma handles the computation while Ethereum provides the final word on asset ownership and dispute resolution. This clean separation means Plasma doesn't need to maintain the same decentralization or validator set that settlement requires, allowing it to make different tradeoffs around operator structure or consensus that would be unacceptable for a settlement layer. The result is a system where each component does one job exceptionally well rather than multiple jobs adequately, unlocking scalability without compromising the security properties that matter most for final asset settlement.
