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Architecture

Celo’s architecture is a multi-layered system that includes a Layer 2 blockchain, core smart contracts, user applications, and a dynamic network topology, all optimized for scalability, security, and ease of use.

Introduction to the Celo Stack

The Celo stack consists of three main components that work together to deliver a seamless blockchain experience:

Celo Blockchain​

The Celo blockchain operates as a Layer 2 (L2) solution using the OP Stack, with distinct layers for optimal performance and security:

  • Execution Layer: EVM-compatible, allowing easy deployment of Ethereum smart contracts.
  • Data Availability Layer: Utilizes EigenDA to ensure transaction data is accessible and cost-efficient.
  • Settlement Layer: Leverages Ethereum to finalize transactions, benefiting from its security.

Celo Core Contracts​

Celo Core Contracts are essential smart contracts on the Celo blockchain, managed through decentralized governance. Key contracts include:

  • Attestations: Links users' phone numbers to their blockchain addresses for secure identity verification and Social Connect features.
  • Governance: Allows community voting on protocol upgrades and changes.
  • StableToken (e.g., cUSD, cEUR): Manages native stablecoin issuance and stability for seamless transactions.
  • Exchange: Facilitates asset trading and liquidity within the Celo ecosystem.
  • SortedOracles: Provides external data, like price feeds, critical for stability and DeFi applications.
  • Validators: Manages validator operations and network security.

Applications​

The Application Layer connects users directly to the blockchain. Developers can build user-friendly applications that are secure, transparent, and decentralized by utilizing Celo’s blockchain.

Our Network Topology​

The Celo network topology consists of various nodes running the Celo blockchain software in different configurations to support the decentralized infrastructure of the network.

Sequencers​

Sequencers replace the traditional validator role in the L2 architecture. They are responsible for:

  • Gathering transactions from other nodes
  • Executing associated smart contracts to form new blocks
  • Submitting these blocks to the Ethereum L1 for final settlement

Sequencers operate on a faster 2-second block time, improving transaction speed and throughput.

Full Nodes​

Full nodes in the Celo L2 network serve multiple important functions:

  • Relaying transactions and responding to queries from light clients
  • Maintaining a copy of the L2 blockchain state
  • Interacting with Ethereum L1 to read and verify L2 block data
  • Optionally running an Ethereum node or using a third-party Ethereum node service

Full nodes can join or leave the network at any time, providing a decentralized infrastructure for the network.

Light Clients​

Light clients, such as those running on mobile apps with limited data, continue to play a crucial role:

  • Connecting to full nodes to request account and transaction data
  • Signing and submitting new transactions
  • Operating without maintaining a full copy of the blockchain state

Light clients benefit from the improved speed and lower costs of the L2 architecture while maintaining a similar user experience.

Data Availability Layer​

Celo L2 incorporates EigenDA as its Data Availability (DA) layer:

  • Ensures transaction data remains accessible and cost-efficient
  • Operates separately from the execution and settlement layers
  • Contributes to lower transaction costs and improved scalability