# Farcaster's Structure By [huhyun](https://paragraph.com/@huhyun) · 2024-10-13 --- Farcaster operates using **Hubs** as key components for data transmission and storage, bridging communication between compatible blockchains like **Optimism** and **Ethereum**. Its architecture consists of three layers: **off-chain data**, **on-chain identity**, and **applications**. ### **Off-Chain Data Layer** The off-chain system is a **peer-to-peer network of Hubs** that store user data. Most user actions are processed and stored within these Hubs, including: * Posting new content. * Following other users. * Reacting to posts. * Updating profile pictures. ### **On-Chain Identity Layer** Farcaster’s on-chain system is deployed on the **Optimism mainnet** to ensure **security and data consistency**. On-chain actions are kept minimal to reduce costs and optimize performance, and include: * Creating new accounts. * Paying for data storage. * Adding account keys for connected apps. ### **How Farcaster Works** Hubs function as **distributed, peer-to-peer servers** for validating and storing off-chain data. Users can set up their own Hub by installing it on a **VPS**. Each Hub synchronizes both on-chain data from Ethereum and off-chain data from other Hubs, storing a full copy of Farcaster’s data accessible via APIs. When a **validator node** is involved, it ensures the integrity of every action within the Hub network. For example, when a user posts a message, it is signed with their account key. The message is then sent to a Hub, where validators verify it through **signature checks and property validation**. After validation, the message is stored locally, replicated across other Hubs, and synchronized with both the **Layer-2 Optimism** and **Layer-1 Ethereum** databases. This structure ensures secure, efficient data management while maintaining **decentralized storage** and network-wide synchronization. --- *Originally published on [huhyun](https://paragraph.com/@huhyun/farcasters-structure)*