Celestia Sparks 'Modular' Wave: Is Polkadot a Modular Blockchain?

Here’s an article we’ve published on PolkaWorld’s Chinese channel, based on our understanding of DA blockchains and the comparison with Polkadot. We’ve translated it into English to discuss this topic with a broader range of developers within the Polkadot ecosystem. If there are any inaccuracies or points that need clarification, please feel free to point them out or raise questions. We look forward to engaging in more discussions!

The launch of Celestia has sparked significant industry attention and fueled the trend of ‘modular blockchains.’ Recently, the NEAR blockchain also announced its entry into the modular blockchain space with the NEAR DA (Data Availability) layer.

So, what exactly is the recently popularized ‘modular blockchain’? Is Polkadot a modular blockchain? How do they differ?

What is a ‘Modular Blockchain’ like Celestia?

The ‘modular blockchain’ we discuss here refers to those like Celestia, Avail, EigenDA, etc., in the Ethereum ecosystem.

In contrast, a ‘monolithic blockchain’ integrates multiple core responsibilities in one chain, such as Bitcoin and Ethereum. These responsibilities include:

  • Execution: Supporting transaction execution, smart contract deployment, and interaction.
  • Data Availability: Ensuring the availability of transaction data.
  • Consensus: Authorizing the content and order of transactions.
  • Settlement: Finalizing transactions, resolving disputes, and bridging between different execution layers.

Monolithic blockchains manage all these responsibilities, leading to scalability issues and higher costs.

Modular blockchains, on the other hand, separate these responsibilities into independent layers (modules), enhancing scalability and reducing costs. For instance, ZK Rollups and Optimistic Rollups outsource the execution layer, while Celestia and Avail focus on outsourcing the Data Availability (DA) layer.

Ethereum itself is seeking to improve scalability with Proto-Danksharding technology (EIP-4844).

In summary, within the Ethereum ecosystem, ‘modular blockchain’ is a technological solution birthed to enhance Ethereum’s scalability. It separates the blockchain’s execution layer, data availability layer, etc., into different ‘modules.’

Is Polkadot a Modular Blockchain?

In Polkadot, we hear a lot of pallets, but this concept differs slightly from the one mentioned above.

Polkadot is a heterogeneous multi-chain system consisting of a relaychain and various parachains. The relaychain maintains consensus and security for the entire network, while parachains focus on their specific applications and performance. Parachains can interact and transfer data across the network using XCM.

Thus, Polkadot achieves horizontal scalability, where network throughput increases with more parachains. Ongoing asynchronous support development will further enhance scalability, allowing Polkadot’s parachains to reach block times of 6 seconds and support thousands of parachains.

In essence, through its shard architecture, Polkadot has largely addressed scalability bottlenecks. This is why the Polkadot ecosystem rarely discusses Rollups, DA layers, and other scalability solutions.

However, Polkadot is indeed a pioneer in the field of ‘modular blockchains’

> Polkadot Epitomizes ‘Modular Blockchain’

From the description above, it’s clear that Polkadot’s architecture embodies ‘modular’ blockchain principles.

The Relaychain is responsible for security and consensus, while each Parachain focuses on its strengths - for instance, KILT Parachain on identity, and HydraDX Parachain on DEXs. Each Parachain, in essence, is a module. The ecosystem’s Parachains interact through cross-chain messages (XCM), utilizing functionalities offered by other Parachains (modules).

Polkadot is advancing a ‘Minimal Relay Chain’ initiative, offloading certain functions from the Relay Chain to multiple ‘System Parachains,’ thus easing the Relay Chain’s load and enabling it to concentrate better on consensus and security. Polkadot has already transferred asset and on-chain collective functionalities to System Parachains, with plans to shift governance, staking, and transfers too. Each System Parachain is essentially a ‘module’ in the blockchain, enhancing Polkadot’s scalability through modularization.

> Modular Blockchain Development Framework: Substrate

Polkadot’s Substrate framework is a modular, open-source platform for blockchain development. It offers highly flexible and customizable modules, allowing developers to tailor the operational logic of their blockchains.

In Substrate, modules are called Pallets, which are predefined functional modules. Thus, Substrate serves as a ‘blockchain Lego,’ enabling developers to swiftly construct blockchains that meet their specific needs using existing modules. Developers can also create their own Pallets for easy integration by other chains.

Currently, the Substrate framework includes numerous functional Pallets, such as:

  • pallet_assets: Offers a simple and secure method for handling fungible tokens.
  • pallet_bounties: Manages rewards for completing specified tasks or objectives.
  • pallet_collective: Allows a group of account IDs to express their collective will through a dedicated origin.
  • pallet_alliance: Establishes a collective of community members for creating rules against misconduct and recognizing teams contributing to the ecosystem. Learn more here.

These are just a few examples of the commonly used Pallets, with many more available, offering a variety of functionalities. The list of Pallets is continually growing, check the latest here.

Recently, Parity merged the Substrate, Polkadot, and Cumulus codebases into the Polkadot SDK. The Polkadot SDK is a blockchain software development toolkit for the Polkadot network, making it easier for developers to create their Parachains, fostering innovation and customization in blockchain.

The Polkadot SDK includes three main software components:

  • Polkadot: The node implementation for the Polkadot network, written in Rust and based on the Substrate framework. The Polkadot directory contains runtime code for Polkadot, Kusama, Westend, and Rococo networks.
  • Substrate: A blockchain development framework offering modular and flexible features for customizing blockchain functionalities and logic. The Substrate directory contains Substrate’s core libraries and pallets, along with sample projects and tools.
  • Cumulus: A suite of tools for writing Substrate-based Polkadot Parachains, enabling developers to leverage Polkadot’s consensus and security for their blockchain applications. The Cumulus directory contains Cumulus’s core libraries and modules, as well as sample projects and tools.

Could Polkadot Introduce a DA Layer?

In theory, Polkadot could decouple data availability as a separate DA layer, thereby expanding into a larger market. However, this would require discussion and consensus from the Polkadot community and developers. Some community members have already engaged in spirited discussions about this on the Polkadot forum.

Moreover, leveraging Polkadot’s ‘modular’ development advantages, a dedicated data availability blockchain could be developed. In fact, this is already being pursued. The Avail project by Polygon, a data availability blockchain, was developed using Polkadot’s Substrate framework and employs the same GRANDMA + BABE consensus as Polkadot.


Modular blockchain is a technological solution that separates different responsibilities of a blockchain into specialized, independent layers, enhancing scalability and performance.

In the Ethereum ecosystem, modular blockchain solutions, such as ZK Rollup, Optimistic Rollup, Celestia, and Avail, primarily address Ethereum’s scalability challenges.

In the Polkadot ecosystem, modular blockchain is intrinsic to Polkadot’s nature. Through its multi-chain architecture and the ‘modular’ development framework Substrate, Polkadot achieves innovation and customization in blockchain technology. Polkadot might also explore launching its own DA layer to broaden its market reach.

Overall, modularization represents a significant trend in blockchain technology, meriting continued attention and exploration.


It appears “modular” means an incomplete design which winds up inefficient, due to security assumption miss-match caused by incompleteness, and also lacks a security definition for messaging.

We optimized bandwidth by tightly coupling availability to approval checking. If you “decouple availability” then availability should become more expensive, maybe in multiple senses, or less secure which requires analysis. If you’ve an optimistic roll up then you’ll pay some hefty latency price too.

If someone presents an optimistic roll up design which looks efficient and sane, then yes we’ll help them build it, but so far nothing.

We’ve plenty of more important much easier projects, like nobody doing real state channel work or faster storage. We expect 4 x improvement by fixing storage. We expect a dramatic improvement by using state channels, given state channels are bitcoin’s entire scaling story. An optimistic roll up has a similar unlocking delay down sides as state channels, but handles more diverse tx types and typically lacks a security model. We also know the stupid simple way of pre-committing to schnorr nonces, and limiting token flow, which also prevents double spending.


All that said, DP SNARKs could maybe be adapted to our erasure coding, or visa versa, which maybe gives something interesting, at least for PR if not for real usage. At least if anyone starts building upon DP SNARKs then folks should try convincing them that substrate makes a better sequencer (because polkadot solves problems similar to sequencers).