Ethereum Scaling with Rollups

Layer 2

The problem is, that transaction speed suffers when the network is busy, making the user experience poor for certain types of dapps. And as the network gets busier, gas prices increase as transaction senders aim to outbid each other. This can make using Ethereum very expensive.

Rollups

Rollups are one of the most promising categories of Layer 2 solutions. These solutions move transaction computations off-chain, but store transaction data to the Ethereum chain, which means that rollups are secured by Layer 1.

  • Optimistic rollups: assumes transactions are valid by default and only runs computation, via a fraud proof, in the event of a challenge.
  • Zero-knowledge rollups: runs computation off-chain and submits a validity proof to the chain.

Optimistic rollups

Optimistic rollups sit in parallel to the main Ethereum chain on layer 2. They can offer improvements in scalability because they don’t do any computation by default. Instead, after a transaction, they propose the new state to Mainnet or “notarise” the transaction.

Zero-knowledge rollups (ZK-rollups)

Zero-knowledge rollups (ZK-rollups) bundle (or “roll-up”) hundreds of transfers off-chain and generate a cryptographic proof. These proofs can come in the form of SNARKs (succinct non-interactive argument of knowledge) or STARKs (scalable transparent argument of knowledge). SNARKs and STARKs are known as validity proofs and get posted to layer 1.

Conclusions

Rollups are a powerful new layer-2 scaling paradigm, and are expected to be a cornerstone of Ethereum scaling in the short and medium-term future (and possibly long-term as well). They have seen a large amount of excitement from the Ethereum community because unlike previous attempts at layer-2 scaling, they can support general-purpose EVM code, allowing existing applications to easily migrate over. They do this by making a key compromise: not trying to go fully off-chain, but instead leaving a small amount of data per transaction on-chain.

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