> For the complete documentation index, see [llms.txt](https://docs.zk.link/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zk.link/architecture/sequencing-layer.md). # Sequencing Layer The sequencing layer is a pivotal component in rollup systems, primarily responsible for receiving user transactions, sequencing the transactions and bundling them into batches. These batches are then committed to the settlement layer. Additionally, in scenarios where the system employs an external DA layer, the sequencer also ensures efficient transmission of transaction data to the DA layer. Similar to other rollups, App Rollups will start with a centralized sequencer model. While this approach offered certain development efficiencies, it also presents challenges and risks, such as potential single point of failure, transaction censorship and issues around miner extractable value (MEV), affecting network fairness and transparency. To address these concerns, zkLink X aims to incorporate decentralized sequencer solutions. These solutions, including platforms like Espresso, Astria, and Fairblock, aim to mitigate centralization risks by processing and validating transactions across a distributed node network. This strategy will not only boost network security and transparency but also strive to offer a more secure, equitable, and efficient rollup solution to its users. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.zk.link/architecture/sequencing-layer.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.