> ## Documentation Index
> Fetch the complete documentation index at: https://docs.polygon.technology/llms.txt
> Use this file to discover all available pages before exploring further.

# Polygon CDK FAQs

> Frequently asked questions about Polygon CDK, covering execution clients, rollup modes, and Agglayer integration.

## What is the Polygon CDK?

Polygon Chain Development Kit (CDK) is a toolkit for launching Ethereum Layer 2 chains with native Agglayer connectivity. It supports **op-geth** and **op-reth** execution clients, giving operators flexibility in performance tuning and resource usage.

## What execution clients does CDK support?

CDK supports two execution clients:

* **op-geth**: Geth-based client with OP Stack architecture and broad tooling support.
* **op-reth**: Reth-based client optimized for high throughput and lower resource consumption.

Both are supported by Conduit and Gateway for production deployments.

## What is a sovereign chain in CDK?

A sovereign chain operates without a prover. Instead, it uses pessimistic proofs via Agglayer to enforce safety and ensure that no chain can withdraw more than it deposits. This enables secure, low-cost execution with fast finality. Sovereign mode is the default configuration.

## What rollup modes are available?

Every CDK chain supports three operating modes:

* **Sovereign**: Agglayer connectivity secured by pessimistic proofs. No prover required.
* **Validium**: ZK-secured execution with offchain data availability via a DAC.
* **zkRollup**: Fully onchain ZK rollup for maximum security and Ethereum-aligned trust.

## How does Agglayer fit into Polygon CDK?

Agglayer is a native feature of every CDK chain. It enables cross-chain interoperability, unified liquidity, and shared state across the connected network. CDK chains are connected to Agglayer by default.

## How can I start building with CDK?

Use the CDK quickstarts to deploy a local testnet. For production-ready deployments, contact [**Conduit**](https://conduitxyz.typeform.com/to/CrvgqEeA?utm_source=polygonannouncement\&utm_medium=partnerblog) or [**Gateway**](https://share.hsforms.com/1toN701PtTBCpyc3bKQBCRAcy6wj?referrer=12118007123).