Ordered parallel transaction execution for the engine. The processor schedules work across SVM executors and commits results through Keeper, preserving input order for conflicting accounts while allowing independent work to run in parallel.
Request completion distinguishes admission rejection from committed execution. Fire-and-forget submission does not provide an execution result. Live observers are separate from request completion and cannot delay its acknowledgment.
Block boundaries drain preceding execution before publication. Replication and recovery validate the same ordered transaction history rather than replacing upstream signatures. Local replay restores account state and cached results without appending duplicate history or publishing live transaction notifications.
An execution barrier drains in-flight work and holds later execution until the caller releases it. This gives snapshots, state checks, and shutdown a coherent boundary. A block-boundary checkpoint must pause execution before later transactions can change the sampled state.
The execution path relies on this exclusion when using borrowed account storage. Simulation runs independently and must retain its own protection against storage relocation.
Simulation executes against account copies and returns an execution record without committing account changes or appending history. It shares the engine's runtime environment but is not a substitute for admission and committed execution.