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Parachain Architecture Overview

Recall that parachains are shards in the relay chain network. Each parachain defines a runtime, or state transition function, specific to their parachain. A relay chain without parachains is not helpful from a user's perspective, as parachains provide application-specific platforms that can work in parallel.

Examples of Existing Parachains​

Many existing parachains on Polkadot and Kusama all of which harness the relay chain's validation schemes to facilitate their application-specific parachains. Some are system parachains, which fulfill some specific functionality for the ecosystem. Below are examples of these system parachains:

  • Asset Hub - a generic assets parachain that provides functionality for deploying and transferring assets — both Fungible and Non-Fungible Tokens (NFTs).
  • Bridge Hub - a parachain that contains the logic needed for bridging to other relay chains or ecosystems.
  • Collectives - The Collectives chain hosts on-chain collectives that serve the Polkadot network. These on-chain collectives will play essential roles in the future of network stewardship and decentralized governance.

Cumulus - Parachain Development Kit (PDK)​

The chains mentioned above use Cumulus to build their parachains. Cumulus is a parachain development kit that uses Substrate and FRAME to make building parachains a streamlined process for a developer.

More notably, besides providing the necessary tools for building a Substrate runtime, Cumulus provides the means to fulfill the requirements for validating blocks supplied from collators to the relay chain.

Relation to Substrate & FRAME​

Although this diagram is simplified, this is essentially the relationship between these tools. For more information, refer to the documentation for Substrate, FRAME, and Cumulus.

For a more detailed diagram, refer to the official Substrate documentation.