Why Rollups Reduce Base-Layer Congestion

Rollups reduce base-layer congestion by moving transaction execution off the base layer and sharing the cost of publishing data across batches.

Instead of Ethereum (the base layer, or L1, that secures the final record) executing every swap, transfer, and contract call, a rollup executes them on a Layer 2 network anchored to Ethereum. A sequencer, the operator that orders transactions, runs them and posts one compressed batch plus a compact state fingerprint to L1.

What actually moves

A rollup replaces many L1 executions with one data-publication transaction. Ethereum receives enough data for nodes to reconstruct the L2 state. A ZK rollup also submits a validity proof, a cryptographic proof that the batch followed the rules; an optimistic rollup posts an assertion and allows challenges backed by fraud proofs. Computation moves away, while data availability—the ability to obtain data needed to rebuild the chain—and settlement stay on the base layer.

For an Automated Market Maker (AMM), a contract that prices swaps from token pools, pool-state changes execute inside the rollup rather than as separate Ethereum calls. An AMM example is syncswap: its state-changing call follows that execution-and-batch path.

What the fee really measures

Rollup fees are lower because fixed L1 costs are divided across a batch, not because the work disappears. The number changes with:

• Ethereum demand for block space and blob space;
• batch compression and transaction count;
• proof generation and verification; and
• the rollup’s execution and sequencer fee.

Blobs, temporary Ethereum data containers introduced by the Dencun upgrade, make rollup publication cheaper than ordinary calldata, but their fee market can still rise.

What to do differently

When an application supports a rollup, use MetaMask, a transaction-signing wallet, to select the correct L2 network, bridge funds if needed, and compare its fee with Ethereum’s. ZK Stack, a toolkit for building ZKsync chains, shows the shift: applications can share Ethereum’s settlement without competing for every unit of Ethereum execution. The trade is dependence on the sequencer and the continuing cost of posting data to Ethereum. Rollups reduce congestion by turning many base-layer executions into a smaller, amortized settlement workload.