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This section of the docs provides a detailed analysis of the full topology of the Polygon zero-knowledge system architecture.

Tailored for CDK stacks and using zkEVM technology, these documents explore the contents, layout, and interactions among component systems and functions. They offer in-depth descriptions of the components that constitute the larger system, with references to relevant code bases.

The diagram below is a full and detailed topological overview of the entire Polygon zero-knowledge system architecture.

Architectural topology

Polygon systems topology


  • Smart contracts: L1 and L2 Solidity smart contracts used for interacting with the whole stack. See the discussion on zkEVM smart contracts for more information.
  • Exit root trees: Append-only sparse Merkle trees which record the current and historical state of the system. See the discussion on zkEVM exit trees for more information.
  • CDK and zkEVM nodes containing:
    • JSON RPC client: Exposes the read/write interfaces for interacting with a node/chain.
    • Pool database: The pool database records transaction requests coming in from the JSON RPC client and sends them to the sequencer.
    • State database: The state database responds to read requests from the JSON RPC client.
    • Sequencer: Does the complex job of carefully sequencing transactions as they come in before sending them to the aggregator for batching. See the discussion on sequencers for more information.
    • Aggregator: Used for aggregating transaction batches to send to the prover. See the discussion on aggregators for more information.
    • Synchronizer: This component ensures a synchronized state between the node’s systems and the L1 outside-world via the Etherman component and the state database.
    • Etherman component: The Etherman helps the synchronizer maintain a synchronized state with L1 by communicating with the L1 Ethereum chain via smart contract methods.
  • Bridge service component: Provides an API to perform bridge claims, i.e. asset and message transfers between L1/L2 and L2/L2.
  • Prover component: System for calculating zero-knowledge proofs on transaction batches.

What to expect

When complete, this section will include information on:

  • The structure of a CDK node and how it interacts with L2 and L1 smart contracts.
  • The structure of a zkEVM node and how it interacts with L2 and L1 smart contracts.
  • The key components included in the nodes, how they function, and their interactions with other components, external dApps, and the L1/L2 environment.
  • Key similarities and differences between a CDK and zkEVM node.
  • CDK validium components, including the DAC and DAC sequencer.
  • Detailed description of the Polygon smart contract sets for L1 and L2.
  • The zkProver and how it interacts with a zkEVM node aggregator.

Currently out of scope

  • The in-development bridge service.
  • AggLayer.