What Is a Modular Blockchain? What Is Celestia Used For?

The modular blockchain represents a major paradigm shift in blockchain architecture design. Unlike traditional "monolithic blockchains" that concentrate all functions on a single chain, a modular blockchain decomposes core functions into independent, specialized layers, with the most suitable solution handling each one. This philosophy of "division of labor" is reshaping how blockchains scale and how their ecosystems develop.

1. From Monolithic to Modular

1.1 The Limitations of Monolithic Blockchains

Traditional blockchains (such as Bitcoin and Ethereum L1) are monolithic — a single chain is simultaneously responsible for all core functions:

Function	Description
Execution	Processes and validates transactions; runs smart contract logic
Consensus	Nodes reach agreement on transaction order and validity
Data Availability	Ensures transaction data can be obtained and verified by anyone
Settlement	Finalizes transactions and resolves disputes

Coupling all functions onto a single chain means:

• Performance bottlenecks: Every node must perform all functions, limiting overall throughput.
• Optimization difficulties: Improving one function may negatively affect others.
• Poor flexibility: Application developers cannot choose the most suitable tech stack for their needs.
• High node requirements: Full-featured nodes have high hardware requirements, which can affect decentralization.

1.2 The Core Idea of Modularity

The principle of modular blockchains is to decouple these four core functions and have specialized layers handle each one — much like the microservices architecture in traditional software engineering, where each service focuses on its own responsibility and collaborates through standard interfaces.

Analogy: A monolithic blockchain is like a single athlete competing in a triathlon; a modular blockchain is like a relay team where each member focuses on the leg they do best.

1.3 Ethereum's Modular Transition

Ethereum is evolving from a monolithic chain to a modular architecture:

Function	Ethereum's Current Approach
Execution	Delegated to Layer 2 (Arbitrum, Optimism, zkSync, etc.)
Consensus	Ethereum Beacon Chain (PoS)
Data Availability	EIP-4844 Blob space (Proto-Danksharding)
Settlement	Ethereum L1

Vitalik Buterin has positioned Ethereum's future as a "rollup-centric roadmap" — Ethereum L1 serves as the settlement and data availability layer, while execution is handled by L2.

2. The Four Core Layers

2.1 Execution Layer

The execution layer is responsible for processing transactions and running smart contracts. In a modular architecture, this is typically handled by rollups or application-specific chains.

Characteristics:

• Determines the user experience (Gas fees, transaction speed)
• Can be optimized for specific use cases (e.g., high-frequency trading, gaming)
• Multiple execution layers can run in parallel, increasing overall throughput

Examples:

• General-purpose execution layers: Arbitrum, Optimism, zkSync (support arbitrary smart contracts)
• Application-specific execution layers: dYdX chain (focused on derivatives trading), Immutable X (focused on gaming and NFTs)

2.2 Consensus and Sequencing Layer

Responsible for determining transaction order and validity.

Current state: Most L2s use centralized sequencers to order transactions. While efficient, this creates a single point of failure and censorship risk.

Development direction:

• Decentralized sequencers: Multiple sequencer nodes collaboratively order transactions through a consensus mechanism.
• Shared sequencers: Multiple rollups share the same set of sequencers, enabling atomic cross-rollup interactions. Key projects: Espresso Systems, Astria.

2.3 Data Availability Layer (DA Layer)

The data availability layer ensures that transaction data is published and accessible to anyone — a prerequisite for verifying the correctness of transactions.

Why does data availability matter?

In the rollup model, transactions are executed off-chain, but transaction data must be published to a reliable location so that:

• Anyone can verify the correctness of rollup state
• In Optimistic Rollups, validators need the data to submit fraud proofs
• Users can reconstruct state and withdraw assets if the sequencer fails

Comparison of major approaches:

Approach	Cost	Security	Examples
Ethereum Calldata	High	Highest (Ethereum security)	Early rollups
Ethereum Blob (EIP-4844)	Medium	Highest	Current mainstream rollups
Celestia	Low	High (independent consensus)	Multiple rollups
EigenDA	Low	High (restaking security)	Some rollups
Avail	Low	High (independent consensus)	In development
Off-chain DAC	Lowest	Low-Medium (committee-dependent)	Validium

2.4 Settlement Layer

The settlement layer is responsible for final confirmation of state transition correctness and dispute resolution.

Advantages of Ethereum as a settlement layer:

• Highest economic security (tens of billions of dollars in staked ETH)
• The broadest network effects and liquidity
• The most battle-tested smart contract platform

Some projects are also exploring alternative settlement solutions, such as using Bitcoin as a settlement layer (the BitVM approach) or purpose-built settlement chains.

3. Celestia: Pioneer of Data Availability

3.1 Celestia's Core Design

Celestia is the first purpose-built modular data availability layer, launching its mainnet in October 2023.

Core innovations:

Data Availability Sampling (DAS):

• Light nodes only need to download random small fragments of a block to verify the data availability of the entire block with high probability.
• No need to download the full block, dramatically reducing node bandwidth and storage requirements.
• As the number of light nodes increases, the network can safely increase block size, achieving linear scaling.

Namespaced Merkle Tree (NMT):

• Each rollup's data is assigned to a dedicated namespace.
• Rollup nodes only need to download data for their own namespace, rather than all data.

3.2 The Celestia Ecosystem

Rollups that use Celestia as their DA layer are called "Sovereign Rollups" or Celestia-DA rollups:

• Reduces data publishing costs for rollups (compared with publishing directly to Ethereum)
• Allows rollups to more flexibly choose their execution environment and settlement layer
• Multiple rollups based on Celestia DA have launched or are in development

3.3 The TIA Token

• Uses: Paying data publishing fees, staking to participate in consensus, governance voting.
• Inflation model: Initial annual inflation rate of 8%, decreasing gradually to 1.5%.

4. Other Important Modular Projects

4.1 EigenDA

EigenDA is developed by the EigenLayer team, leveraging Ethereum's restaking security to provide data availability services.

Key features:

• Borrows the economic security of Ethereum validators
• Does not require independent token staking
• Lower cost than Ethereum L1 with security derived from Ethereum

4.2 Avail

A modular DA project founded by former Polygon members.

Key features:

• Uses KZG commitments and DAS technology
• Supports multiple execution environments
• Provides Avail Nexus as a unified verification layer across rollups

4.3 Dymension

A modular platform focused on "RollApps" — easily deployable, application-specific rollups.

Key features:

• Built on the Cosmos SDK
• Provides a RollApp development tool (Roller)
• Built-in IBC cross-chain communication
• Serves as the settlement layer and liquidity hub for RollApps

4.4 Rollup-as-a-Service (RaaS)

RaaS platforms allow any project to easily deploy its own rollup without building infrastructure from scratch:

Platform	Highlights
Caldera	Supports OP Stack and Arbitrum Orbit
Conduit	One-click L2/L3 deployment
AltLayer	Elastic rollup-as-a-service
Gelato	Automation and RaaS platform

5. The Modular vs. Monolithic Debate

5.1 Advantages of Modular

Advantage	Description
Flexibility	Each layer can be independently optimized and upgraded
Scalability	Multiple execution layers run in parallel, enabling linear scaling
Customization	Applications can choose the tech stack best suited to their needs
Lower barrier	RaaS makes launching new chains simple
Specialization	Each layer handled by the most capable team and technology

5.2 The Monolithic Counterargument

Some projects (such as Solana) advocate for the advantages of a monolithic (integrated) approach:

Advantage	Description
Low latency	Avoids cross-layer communication delays
Composability	Applications on the same chain can interact atomically in sync
Simplicity	Users and developers deal with a single environment
Proven track record	Monolithic chains have years of operational history

5.3 The Reality

In practice, modular and monolithic are not an either-or choice:

• Ethereum is moving toward modular (L1 + L2 + DA layer)
• Solana continues to optimize performance on its monolithic architecture
• The Cosmos ecosystem is inherently modular
• The two paths may ultimately converge

6. Challenges of Modular Architecture

6.1 Fragmentation

Modularity has produced a large number of rollups and chains, leading to:

• Liquidity fragmentation: Assets and liquidity are spread across multiple chains.
• User experience fragmentation: Users need to manage assets and operations across many chains.
• Developer fragmentation: Developers face difficult choices about which chain to deploy on.

Solutions: Chain abstraction, shared sequencers, and cross-rollup communication protocols.

6.2 Security Assumptions

Modular architecture introduces multi-layer security assumptions. Overall security depends on the weakest link:

• Is the data in the DA layer truly available?
• Are shared sequencers reliable?
• Is cross-layer communication secure?

6.3 Latency and Complexity

Cross-layer communication adds latency and system complexity. In scenarios that require low latency and atomicity, this can be a limiting factor.

6.4 Cross-Layer MEV

In modular architecture, the extraction and distribution of MEV (Maximum Extractable Value) becomes significantly more complex, involving a strategic interplay among sequencers, execution layers, and settlement layers.

7. Development Trends in Modular Blockchains

7.1 Full Danksharding

Ethereum's full Danksharding will introduce more Blob space and DAS mechanisms, greatly improving Ethereum's capacity and efficiency as a DA layer.

7.2 DA Layer Competition

Ethereum Blob, Celestia, EigenDA, Avail, and other DA solutions will compete, driving data publishing costs continuously lower.

7.3 Widespread Adoption of Shared Sequencers

Shared sequencers will allow multiple rollups to achieve atomic cross-rollup transactions and interoperability, easing fragmentation.

7.4 Explosive Growth of Rollups

RaaS lowers the barrier to launching rollups, and a large number of application-specific and community-specific rollups are expected to emerge.

7.5 Standardization of the Modular Stack

Interface and communication standards between different modules will gradually converge, promoting ecosystem interoperability and composability.

Summary

The modular blockchain represents a paradigm shift in blockchain architecture design from "broad and all-inclusive" to "specialized and precise." By decoupling execution, consensus, data availability, and settlement functions into specialized layers, modular architecture has the potential to simultaneously improve performance, flexibility, and scalability. The emergence of data availability layers like Celestia and EigenDA, and the maturation of Rollup-as-a-Service platforms, are bringing the modular vision from theory to practice. Understanding the design philosophy of modular architecture and the role of each layer is key to grasping the direction of blockchain technology.

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