OP Stack

What is OP Stack?

According to the official explanation from OP Stack Docs, the OP Stack is the standardized, shared, and open-source development stack that powers Optimism, maintained by the Optimism Collective.The OP Stack is the set of software that powers Optimism — currently in the form of the software behind Optimism Mainnet and eventually in the form of the Optimism Superchain and its governance.With the advent of the Superchain concept, it has become increasingly important for Optimism to easily support the secure creation of new chains that can interoperate within the proposed Superchain ecosystem. As a result, the OP Stack is primarily focused around the creation of a shared, high-quality, and fully open-source system for creating new L2 blockchains. By coordinating on shared standards, the Optimism Collective can avoid rebuilding the same software in silos repeatedly.Although the OP Stack today significantly simplifies the process of creating L2 blockchains, it’s important to note that this does not fundamentally define what the OP Stack is. The OP Stack is all of the software that powers Optimism. As Optimism evolves, so will the OP Stack.The OP Stack can be thought of as software components that either help define a specific layer of the Optimism ecosystem or fill a role as a module within an existing layer. Although the current heart of the OP Stack is infrastructure for running L2 blockchains, the OP Stack theoretically extends to layers on top of the underlying blockchain including tools like block explorers, message passing mechanisms, governance systems, and more.Layers are generally more tightly defined towards the bottom of the stack (like the Data Availability Layer) but become more loosely defined towards the top of the stack (like the Governance Layer).

Three Core Design Principles of the OP Stack

The OP Stack is designed for building L2 blockchain ecosystems, developed by the Optimism Collective. The construction of the OP Stack adheres to three main principles: Utility, Simplicity, and Extensibility, each crucial for the stack's effectiveness and alignment with the goals of the Optimism platform.

Utility

Software must significantly benefit the Optimism Collective to be included in the OP Stack. It should support and enhance the capabilities of the platform, such as a robust open-source block explorer that allows users to inspect the Superchain. Moreover, there's a focus on encouraging innovative and bold ideas that might not immediately seem practical but contribute to a vibrant and dynamic ecosystem.

Simplicity

Simplicity in the OP Stack helps minimize engineering overhead, allowing developers to focus more on innovation rather than complexity. The use of battle-tested components, such as Geth for execution, underscores this principle. A simpler codebase reduces potential errors and makes it easier for external contributors and auditors to engage with and improve the system.

Extensibility

OP Stack’s strength is its open and collaborative nature, facilitating shared development efforts and reducing redundant work. The code is designed to be extensible, adhering to open-source norms with permissive licensing, clear APIs, and modular design to encourage other developers to extend and enhance its functionality.

OP Stack Layers

Data Availability

The Data Availability Layer is essential for determining where and how raw input data for an OP Stack-based chain is published. This layer allows for the integration of one or multiple Data Availability modules, which crucially influences the chain's security model. The choice and functionality of these modules play a pivotal role in the chain's ability to maintain security and synchronization. In instances where data becomes inaccessible, it can significantly disrupt the chain's synchronization process, highlighting the importance of informed module selection to ensure the system's overall robustness and security.

Ethereum Data Availability (DA)

The Ethereum Data Availability (DA) module is a prominent choice within the OP Stack. It utilizes various data sources available on the Ethereum blockchain, such as Ethereum calldata, events, and 4844 data blobs. This module is extensively used due to its versatility and comprehensive data support, making it a vital component of the OP Stack. The popularity of the Ethereum DA module also reflects its high effectiveness and seamless integration with the broader Optimism ecosystem, enhancing the functionalities of OP Stack-based chains.Source Code is here.

Sequencing

The Sequencing Layer is crucial for managing the collection and publication of user transactions on an OP Stack chain, particularly concerning the Data Availability Layer modules in use. In the standard Rollup configuration, a Sequencer entity typically handles this responsibility. The Sequencing Layer’s design ensures that transactions are timely processed by imposing limits on the Sequencer’s authority to prevent transaction withholding beyond a specified period. This setup is intended to be modular, giving chains the flexibility to select or change their Sequencing mechanisms to suit evolving needs, thus enhancing adaptability and efficiency within the OP Stack ecosystem.

Single Sequencer

The default configuration for OP Stack employs a Single Sequencer, where a designated actor is responsible for sequencing. This role is regulated by a transparent governance mechanism that helps ensure the system’s security and integrity, with community oversight or designated authorities deciding who fills this essential role.

Multiple Sequencer

An extension of the Single Sequencer model is the Multiple Sequencer approach, where the Sequencer role can be filled by one of several pre-approved actors. This model allows individual OP Stack-based chains to define their own criteria for Sequencer eligibility and selection, providing additional customization and flexibility in the Sequencing process.

Derivation

The Derivation Layer processes the raw data from the Data Availability Layer, converting it into processed inputs that are then sent to the Execution Layer via the standard Ethereum Engine API. This layer is essential for interpreting and transforming raw data, ensuring that the input data aligns with the current system state as defined by the Execution Layer. The flexibility of the Derivation Layer allows it to adapt its processing mechanisms to various data sources, making it a fundamental component in the OP Stack’s architecture for facilitating efficient data interaction and processing.