What is the execution layer?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 5 min
In short
The execution layer is the part that actually processes transactions and updates balances and contract state. On Ethereum it is separated from the consensus layer, and the two communicate over a dedicated interface. A rollup is what you get when only this execution part is moved off layer 1.
Key points
- The part that processes transactions and updates state
- Separated from the consensus side on Ethereum
- The two communicate over a dedicated interface
- A rollup moves only this part off layer 1
Definition
The layer that takes transactions, runs the computation, and updates state such as account balances and contract storage. Which transactions run, and in what order, is decided by the consensus layer.
On Ethereum, the client that processes transactions and the client that proposes and attests to blocks are separate pieces of software. The execution side computes what the state becomes after a set of transactions; the consensus side finalises that result as a block.
The two talk over a dedicated interface called the Engine API. Separating the roles lets improvements to the execution environment and to the consensus rules proceed independently. Running a full node means running both clients.
A rollup can be understood as this execution part lifted out into a chain of its own. Execution happens on layer 2, while layer 1 backs the correctness of the result through proofs or challenges. Discussions of app-chains and modular designs all start from this same separation.
Watch out for
- · Running your own node requires both the execution and consensus clients, or it will not sync
- · Even with the same EVM, chains differ in gas accounting and precompiles, so behaviour is not identical
- · A layer 2's execution result only gains layer 1's guarantees once it is recorded there