### Ethereum’s Scaling Challenges: Optimistic and ZK Rollups
The deluge of new protocols and updates in the blockchain industry can be overwhelming. However, amidst this technological flood, it’s crucial to remember that the primary goal of most blockchain projects is addressing the Blockchain Trilemma — decentralization, security, and scalability.
Ethereum emerged to improve the scalability deficiency of Bitcoin. To this end, Ethereum has continuously rolled out various technical updates aimed at enhancing its decentralization, security, and scalability. Despite these efforts, Ethereum still lags behind centralized systems in terms of transactions per second (TPS) and cost-efficiency. The network’s average TPS remains around 20 to 30, a limitation inherent in blockchain technology that’s not easy to overcome.
To address these scalability issues, Layer 2 solutions, particularly rollups, have been introduced. Fundamentally, blockchains encapsulate encrypted transaction data within blocks and propose these to the network (mainnet). Validators verify and record these transactions to ensure their legitimacy.
An Ethereum block can accommodate approximately 200 transactions, depending on the total gas fees, and takes about 10 seconds to generate. Rollups, however, compile and compress numerous transactions into a single block. Optimistic Rollups, one of the prominent examples, can squeeze between 1,000 and 2,000 transactions into a single Ethereum block. This method significantly boosts Ethereum’s TPS, addressing its scalability issues.
The rollup process requires additional steps, including compiling transaction records, which adds roles like Sequencer and Verifier to the traditional proposer-validator relationship within Ethereum’s network. The Sequencer sorts and consolidates transaction requests, while the Verifier ensures the accuracy of compressed data.
However, if the process of consolidating, sorting, compressing, and verifying transactions takes too long, users face a prolonged wait for transaction completion. Optimistic Rollups were the first-generation solution to this problem. They start by assuming that Layer 2 transactions are valid, execute the transactions, and then verify the legitimacy over a week before compressing and recording them onto an Ethereum block.
The introduction of ZK (Zero-Knowledge) Rollups aimed to eliminate the optimistic perspective. ZK Rollups compress the sequenced transaction list and then apply a Zero-Knowledge proof, akin to a QR code. Verifiers can then use scanners to quickly confirm the accuracy of the transactions without unpacking the entire block, making ZK Rollups an efficient and secure Layer 2 solution.
