Modular Blockchain

Modular vs. monolithic

Two competing architectural approaches:

• Monolithic chains (Bitcoin, Solana, Monad) — single chain handles all functions: execution, settlement, consensus, data availability.
• Modular chains — split functions across specialized layers. Each layer optimized for specific role.

The bet: specialization produces better scaling than monolithic designs.

The four functions

A blockchain's responsibilities:

• Execution — running transactions and computing new state.
• Settlement — finalizing transactions in agreed historical record.
• Consensus — agreeing on transaction ordering.
• Data availability — making transaction data accessible for verification.

Modular designs assign each function to a specialized layer.

Modular stack examples

A typical modular stack:

• Execution layer — a Layer 2 rollup (Arbitrum, Optimism, Base, etc.) executes transactions.
• Settlement layer — Ethereum L1 records final state.
• Consensus layer — Ethereum's PoS validators reach consensus.
• Data availability layer — either Ethereum (most common) or specialized DA chains (Celestia, EigenDA, Avail, Near DA).

This stack lets each layer optimize independently while combining for full blockchain functionality.

Why modular

Several arguments:

• Scaling. Specialized layers can scale better than generalist designs.
• Cost. Cheap data-availability layers reduce L2 costs dramatically (EIP-4844 demonstrated this).
• Flexibility. Different applications can pick different layers.
• Innovation. Each layer can innovate independently without affecting others.

Why monolithic

Counter-arguments:

• Simplicity. Monolithic chains have fewer trust assumptions and fewer moving parts.
• Speed. Avoiding cross-layer coordination produces lower latency.
• Atomicity. All transactions on a monolithic chain are atomic; cross-layer atomicity is hard.
• Composability. Within a single chain, all applications can interact freely; cross-chain interactions add friction.
• Real-world performance. Solana has demonstrated that monolithic designs can scale to high throughput when properly engineered.

Major modular projects

A few:

• Celestia — first major DA-focused layer. Rollups can post data here at lower cost than Ethereum.
• EigenDA — DA layer secured by EigenLayer restaking.
• Avail — Polygon-affiliated DA layer.
• Near DA — Near Protocol's DA service.
• OP Stack — Optimism's framework for building rollups; entire ecosystem of OP Stack chains.
• Arbitrum Orbit — framework for L3 chains settling to Arbitrum.

Major monolithic counter-examples

Chains betting on monolithic scaling:

• Solana — high-throughput single chain.
• Monad — EVM-compatible monolithic chain targeting parallel execution.
• Sui, Aptos — Move-language chains with parallel-execution architectures.
• Hyperliquid — purpose-built monolithic chain for trading.

These argue specialized monolithic designs can scale better than fragmented modular stacks.

Trade-offs

Several real differences:

• Cross-chain UX — modular requires bridges, intent systems, account abstraction. Monolithic has native composability.
• Liquidity fragmentation — modular spreads liquidity across many chains; monolithic concentrates it.
• Developer complexity — modular requires choosing layers; monolithic requires only choosing the chain.
• Security assumptions — modular involves multiple trust layers; monolithic is single-stack.

Where this is heading

Both approaches have legitimate cases:

• Modular thesis dominant in Ethereum ecosystem; Ethereum's roadmap explicitly endorses rollup-centric scaling.
• Monolithic thesis has produced Solana's success and continues with Monad, Sui, Hyperliquid.
• Hybrid models emerging — some chains combine modular elements with monolithic execution.
• Long-term winners likely vary by use case rather than convergence on one model.

What individuals should know

For users:

• Most user activity happens on execution layers (L2s or alt-L1s).
• DA layer choice is mostly invisible but affects cost.
• Cross-layer movement requires bridges with their own complexity.

For developers:

• Modular stacks offer flexibility at cost of complexity.
• Monolithic chains offer simplicity at cost of scaling ceiling.
• Choice depends on application — gaming might prefer monolithic for atomicity; DeFi might prefer modular for cost.

For investors:

• DA-layer tokens (TIA from Celestia) represent bets on modular thesis.
• Monolithic L1 tokens (SOL, MONAD when launched) represent bets on monolithic thesis.
• Both can be right for their respective use cases.

The modular vs. monolithic debate is one of the most consequential architectural questions in crypto. Different camps have legitimate cases; the eventual answer may be that both succeed in different niches rather than one displacing the other.