Rollup, as the current mainstream Layer2 scaling solution, has contributed to Ethereum's pursuit of scalability, and the two Rollup solutions, OptimisticRollup and ZKRollup, have gradually been validated by the market. After this, Layer2 scaling began to welcome the multi-Rollup direction, where anyone can quickly launch their rollup using SDKs, and run applications on the rollup with high performance and low cost. In the future of Layer2 scaling, Rollup is gradually taking the dominant position, and the most important thing in this process is to simplify the way for developers to deploy various types of rollups.

On June 26, zkSync introduced ZK Stack, a modular open-source framework for building zk-powered rollups. ZK Stack is a free, modular open-source framework designed to build custom ZK-supported L2 and L3 (called hyperchains) based on zkSync Era code. Before this, the Optimism team had launched a scalability solution, OP Stack, to create a shared, high-quality, fully open-source system for creating new Layer2 blockchains.

In this article, we will compare the similarities and differences, strengths and weaknesses, and use cases of these two solutions. In the increasingly competitive Layer2 market, who will break through and build greater ecosystem interoperability?

OP Stack

OP Stack is a standardized, shared, and open-source development stack that supports Optimism, maintained by the Optimism Collective. It encompasses three design principles: practicality, simplicity, and scalability. As a public product of the Ethereum and Optimism ecosystem, the OP Stack is composed of many different software components that together form the pillars of Optimism.

Features of OP Stack

OP Stack focuses mainly on creating a shared, high-quality, fully open-source system for creating new Layer2 blockchains. By coordinating shared standards, the Optimism Collective can avoid redundantly rebuilding the same software in isolation. The OP Stack can be seen as a set of software components that can help define specific layers of the Optimism ecosystem, as well as act as modules within existing layers. Although the core of the OP Stack is currently the infrastructure for running Layer2 blockchains, in theory, the OP Stack can be expanded to layers above the underlying blockchain, including block explorers, messaging mechanisms, governance systems, and other tools.

OP divides the blockchain into three major levels: the consensus layer, the execution layer, and the settlement layer. Then it standardizes the three layers. In terms of specific architecture, the OP Stack can be divided into six layers:

DA (Data Availability Layer): The data availability layer defines the source of the raw data for the Layer2 based on the OP Stack. The OP Stack can use one or more data availability modules to obtain its input data. The Ethereum DA is currently the most widely used data availability module in the OP Stack, but more and more other chains can also be integrated in the future.

Sequencing (Sequencing Layer): The sequencing layer determines how to collect user transactions on the OP Stack chain and publish them to the data availability layer module currently in use. In the default Rollup configuration of the OP Stack, sequencing is usually handled by a single dedicated sequencer. The rules defined in the derivation layer often limit the ability of the sequencer to retain transactions beyond a specific time period. In the proposed future, sequencing will be modularized so that chains can easily select and change the mechanism controlling their current sequencer.

Derivation (Derivation Layer): The derivation layer defines how to process the raw data in the data availability layer to form processed inputs. These inputs are sent to the execution layer through the standard Ethereum engine API.

Execution (Execution Layer): The execution layer defines the state structure within the OP Stack system. The execution layer provides an entry point for abstracting to EVM modifications or completely different underlying VMs.

Settlement (Settlement Layer): Used to verify the current transaction results. After confirmation through Layer2, the confirmation information is sent to the target blockchain for final settlement to obtain data validity.

Governance (Governance Layer): The governance layer refers to the general tools and process sets used for managing system configuration, upgrades, and design decisions.

OP's goal is to upgrade to a superchain through this architecture. The OP Stack deconstructs the various components required to build Layer2 chains and packages them as separate modules. Developers can combine the most suitable modules to create their own Layer2, making it easier and more efficient for developers to implement proprietary chains.

Bedrock Upgrade

The completion of the Bedrock upgrade represents a complete modular rewrite of the core components of the OP mainnet Rollup architecture, the launch of the first official version of the OP Stack, and the next major version of the Optimism network. This further narrows the gap between Optimism and Layer1 Ethereum. The Bedrock version will support multiple proof schemes and multiple clients to attract different developers and projects, and will also follow different routes to keep up with technological decentralization while maintaining the decentralization of the governance structure. This provides a key advantage for OP to implement the superchain in the future:

Lower network costs: Optimized data compression strategy, eliminating Gas Fee related to EVM execution when submitting data to L1, can reduce about 10% of additional costs; Reduced deposit wait time: Support for Layer1 reorganization is introduced into the node software, and deposits are expected to be confirmed within 3 minutes; Improved proof modularity: The proof system is abstracted separately from the OP Stack, and you can choose between fault-tolerant proofs or Zk-Snark and other validity proof mechanisms; Improved node performance: By executing multiple transactions in a single rollup block, 15G of data can be reduced each year. Improved Ethereum equivalence: Deleted several deviations from Ethereum in the previous version, and added support for EIP-1559, chain reorganization, and other Ethereum features existing on Layer1. After the Bedrock upgrade is completed, it not only improves Optimism's Layer2 Rollup, but also brings Optimism one step closer to upgrading to a superchain. The next major scalability improvement of the OP Stack is to introduce the concept of superchains: a chain network that shares bridges, decentralized governance, upgrades, communication layers, etc., all of which are built on the OP Stack. The launch of the superchain will merge the Optimism mainnet and other chains into a unified OP chain network, marking an important step towards bringing scalable and decentralized computing to the world.

OP Stack simplifies the process of creating Layer2 blockchains and supports all software of Optimism. As Optimism develops, OP Stack will also develop. The Base Layer2 that Coinbase is preparing to launch this year will be developed based on OP Stack, and BNB Chain has also announced that the opBNB testnet is built based on OP Stack. OP Stack currently appears in the form of software behind the Optimism mainnet, and will eventually appear in the form of the Optimism superchain and its governance.

ZK Stack

ZK Stack is a free, modular, open-source framework designed to build custom ZK-supported L2s and L3s (known as superchains) based on zkSync Era's code. The core of ZK Stack provides two key features: sovereignty and seamless connection. Developers have full rights to the code and unrestricted autonomy to customize and shape every aspect of the chain. Superchains run independently, relying only on Ethereum Layer1 to ensure their liveness and security, while the Super Bridge network facilitates the interconnection of each superchain, thereby achieving trustless, fast, and cheap interoperability. In summary, ZK Stack has three characteristics: open source, composability, and modularity.

ZK Stack Features

Free: ZK Stack is developed under a completely permissive MIT/Apache open-source license, ensuring it is freely available.

Composable: Superchains built using ZK Stack can seamlessly connect in a trustless network with low latency and shared liquidity.

Modular: Customize and shape every aspect of the superchain, from the choice of sequencer and data availability modes to defining unique token economics.

Ultra-Low Cost: Due to the succinctness of ZK proofs, some types of transactions (such as oracle updates) are 1000 times cheaper on ZK Stack than on other rollup platforms. In addition to the ZK rollup mode, ZK Stack can also optionally scale with extremely affordable zkPorter accounts for appropriate use cases.

Tried and Tested: zkSync Era is the most widely adopted ZK rollup on Ethereum, as evidenced by its substantial TVL and transaction volume. With this track record, ZK Stack is a safe choice in terms of security and reliability.

Future-Oriented: ZK rollups are the future of Ethereum scaling. The right architecture is built from the start to fully exploit the potential of ZK superpowers.

ZK Stack Upgrade

The ZK Stack is also a major upgrade for the core zkSync team. The team's perspective has expanded from building ZK technology to helping many teams understand ZK Stack and contribute to it. As more superchains are launched, the number of core contributors will increase, and the community will become the true owner of the zkSync network, especially when building custom superchains. If building a generic DeFi dapp or NFT project, deploying it on existing superchains like zkSync Era will be a simpler process, allowing it to be composably synchronized with other protocols in the ecosystem.

Moreover, ZK Stack allows you to build your own sovereign superchain without sacrificing interoperability and composability. This will greatly enhance the hyper scalability of ZK Stack. Each superchain is seamlessly integrated into its infinitely scalable ecosystem, supported by shared provers and fractal scaling, thus nurturing a complete liquidity network. In this ecosystem, users can transfer assets quickly in a trustless manner without incurring additional costs. Smart contracts will make cross-chain asynchronous calls, and superchains themselves will have sovereignty, enabling them to join alternative ecosystems and take their on-chain assets with them when they choose to leave.

Next, the ZK Stack team will modify the codebase to make it easier to checkout, configure, and deploy ZK Stack instances, achieving the ultimate goal of one-click deployment.

OP Stack VS ZK Stack

The launch of ZK Stack is less about competing with OP Stack than about taking a new multi-chain interaction scenario.

From a technical perspective, the superchains of ZK Stack reuse Ethereum's security and consensus methods to the maximum extent, and can directly rely on Ethereum's security. Compared to OP's interactive fraud proof, ZK proof directly verifies state changes without waiting for state changes on the underlying Ethereum, simplifying the design and avoiding repetitive inputs, improving the efficiency of chain-to-chain interaction. By contrast, OP Stack still has a lot of restrictions on asynchronous cross-chain calls: its state changes need to wait for verification on the underlying Ethereum, and fraud proofs also need to wait for confirmation.

Furthermore, unlike OP stack's focus on the transformation of the Layer2 market, ZK stack aims to encompass both Layer2 and Layer3 markets. Although both want to achieve a multi-chain empire through chain-to-chain interoperability, ZK Stack builds Layer3 and a multi-chain network, aiming to develop highly customized scaling.

From an ecological perspective, OP Stack has the advantage of being first. Shortly after the launch of OP Stack, it received support from many projects. In February of this year, Coinbase announced the launch of a multi-chain Layer2 platform Base built on OP Stack, and will build a superchain with Optimism Collective. Secondly, OP Stack also received support from BNB Chain. On the evening of June 19th, BSC announced a new scalability solution: opBNB, which is implemented based on the Bedrock version of OP Stack and is EVM-compatible. In addition, many application development teams such as NFT trading market Zora, a16z Crypto's client Magi, etc. have also chosen OP Stack to develop application chains.

Compared to this, zkSync's own Layer2 is not yet fully built, and there have always been compatibility issues and downtime problems with ZkRoullup, and the ecology is mostly shitcoin projects, and there is little support from well-known factories and projects. In this regard, zkSync's eagerness to build Layer3 cannot convince the market's recognition.

Conclusion

From the perspective of blockchain scalability, superchains and super scalability are worth paying attention to, but from the current development, the project is still in its early stages, and it is still unknown who can dominate the market with ecological advantages of OP Stack and technical advantages of ZK Stack. However, despite the differences in technology, details, and views, they all have the goal of infinite scalability. A new round of multi-chain scalability narrative for Ethereum is gradually unfolding.

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