An overview of the dominant scaling architectures and their technical trade-offs, forming the foundation for DeFi's next evolution.
LABS
Guides
Future Directions for Layer 2 DeFi Scaling
Chainscore © 2025
current_state
Current State of Layer 2 Scaling
01
Optimistic Rollups
Fraud proofs secure these rollups by assuming transactions are valid unless proven otherwise within a challenge window.
- Sequencers batch transactions off-chain, posting only compressed data to L1.
- Long withdrawal delays (7 days) are required for security, though liquidity providers mitigate this.
- This architecture prioritizes compatibility, enabling near-full EVM equivalence for easier dApp migration.
02
ZK-Rollups
Validity proofs provide cryptographic security by verifying transaction batches with a zero-knowledge proof (SNARK/STARK).
- Instant finality on L1 enables near-instant withdrawals without trust assumptions.
- High computational overhead for proof generation creates centralization pressures for provers.
- EVM compatibility is complex, with zkEVMs achieving varying levels of bytecode equivalence.
03
Validiums & Volitions
These hybrids use ZK-proofs for validity but keep data off-chain, offering a spectrum of data availability (DA) choices.
- Validiums use external DA committees for higher throughput but introduce new trust assumptions.
- Volitions let users choose per-transaction between on-chain (zkRollup) or off-chain (Validium) DA.
- This flexibility optimizes for specific use cases like high-frequency trading or low-cost NFT minting.
04
State Channels & Sidechains
State channels enable instant, private transactions between participants off-chain, settling final state to L1.
- Ideal for high-throughput micropayments or gaming where participants are known (e.g., chess moves).
- Sidechains like Polygon PoS are independent chains with their own validators and security models.
- They offer full EVM compatibility but involve sovereign security trade-offs compared to rollups.
05
Cross-L2 Interoperability
Native bridges, third-party bridges, and shared messaging layers form a fragmented connectivity landscape.
- Canonical bridges are generally most secure but often slower and feature-limited.
- Liquidity fragmentation across rollups necessitates complex bridging and asset wrapping strategies.
- Emerging standards like Chainlink CCIP and LayerZero aim to unify cross-chain communication.
06
Sequencer Centralization
Most rollups rely on a single sequencer to order transactions, creating a critical central point of failure.
- This grants the sequencer powers like transaction censorship and MEV extraction.
- Decentralization roadmaps involve permissionless proposer-builder separation and shared sequencer networks.
- The current state presents a significant security and liveness risk contrary to blockchain ethos.
zk_evolution
The Evolution of ZK-Rollups
Tracing the progression from early validity proofs to modern, application-specific systems and their implications for DeFi scalability.
01
ZK-SNARKs
Succinct Non-interactive Arguments of Knowledge enable efficient proof verification.
- Proofs are small and fast to verify, requiring a trusted setup ceremony.
- Pioneered by Zcash for privacy, later adapted for scaling by early rollups.
- This matters as it established the core cryptographic foundation for proving state transitions off-chain.
02
ZK-STARKs
Scalable Transparent Arguments of Knowledge offer post-quantum security and transparency.
- Eliminates the need for a trusted setup, enhancing decentralization.
- Proof generation is more computationally intensive but scales better with complexity.
- This is crucial for long-term security and for applications requiring massive computational proofs.
03
zkEVMs
Zero-Knowledge Ethereum Virtual Machines execute EVM-compatible smart contracts in ZK-circuits.
- Enables native execution of Solidity contracts without significant redesign.
- Projects like zkSync Era and Polygon zkEVM demonstrate this approach.
- This matters for developers as it preserves the existing tooling and contract ecosystem.
04
Validiums
A scaling solution where data availability is kept off-chain, not posted to Ethereum.
- Offers higher throughput and lower fees than standard rollups by reducing L1 data costs.
- Introduces a data availability dependency on a separate committee or DAC.
- This trade-off is significant for high-frequency, low-value transactions where cost is paramount.
05
Volitions
A hybrid architecture giving users a choice between a ZK-Rollup and a Validium for each transaction.
- Users can opt for maximum security (rollup mode) or minimum cost (validium mode).
- Implemented by StarkNet for flexible security-cost optimization.
- This matters for user sovereignty, allowing tailored security assumptions per asset or action.
06
ZK-Proof Aggregation
The process of batching multiple ZK proofs into a single, verifiable proof.
- Dramatically reduces the on-chain verification cost per transaction.
- Enables efficient interoperability between different ZK-rollup instances.
- This is critical for scaling the number of parallel chains and reducing overall L1 congestion.
Modular Blockchain Architectures
Understanding the Modular Stack
Modular blockchains separate core functions—execution, settlement, consensus, and data availability—into specialized layers. This is a shift from monolithic chains like Ethereum mainnet, which handle all functions in one place. The goal is to achieve superior scalability and flexibility by allowing each layer to be optimized independently.
Key Components
- Execution Layer: Where transactions are processed and smart contracts run (e.g., Optimism, Arbitrum, zkSync).
- Settlement Layer: Provides a finality root and dispute resolution, often the base layer (e.g., Ethereum L1).
- Consensus Layer: Orders transactions and secures the network.
- Data Availability (DA) Layer: Ensures transaction data is published and accessible for verification, critical for rollup security. Projects like Celestia and EigenDA provide this as a service.
Practical Analogy
Think of a monolithic chain as a single, all-in-one factory. A modular stack is like a supply chain: one factory makes parts (execution), another assembles (settlement), a warehouse stores blueprints (DA), and a manager coordinates (consensus). This specialization allows each part to scale and innovate faster.
Cross-L2 and Cross-Chain Interoperability
Comparison of interoperability solutions for asset and data transfer between Layer 2s and other chains.
| Feature / Metric | Native L2 Bridges (e.g., Optimism Gateway) | Third-Party Bridges (e.g., Hop, Across) | Generalized Messaging (e.g., LayerZero, CCIP) |
|---|---|---|---|
Primary Use Case | Withdrawals/Deposits to L1 | Fast L2-to-L2 Swaps | Arbitrary Data & Contract Calls |
Typical Transfer Time | ~7 days (Challenge Period) or ~1 hour (fast exit) | ~1-10 minutes | Seconds to minutes (varies by destination) |
Cost Structure | L1 gas + L2 fee (~$5-$50) | Relayer/Liquidity Provider fees (~$1-$10) | Gas on source/dest chains + protocol fee |
Security Model | Inherits L1 security via fraud/validity proofs | Optimistic or MPC-based with external validators | Decentralized oracle/validator networks |
Capital Efficiency | Low (locked in bridge contracts) | High (liquidity pools enable instant swaps) | High (no locked liquidity for messaging) |
Programmability | Limited to asset transfers | Limited to asset transfers with swaps | Full (arbitrary contract execution) |
Example Throughput Limit | Governed by L1 block gas limit | Governed by liquidity pool depth | Governed by destination chain capacity |
Developer Considerations for Future L2s
Key technical and strategic factors for developers building on next-generation Layer 2 solutions.
1
Evaluate Data Availability and Proof Systems
Assess the core security and cost model of the L2's architecture.
Detailed Instructions
Data Availability (DA) is the foundational guarantee that transaction data is published and accessible. Future L2s may use validiums (DA off-chain with fraud/validity proofs) or volitions (user-selectable DA). Proof systems like zk-SNARKs or zk-STARKs define finality and cost.
- Sub-step 1: Audit the DA layer. Determine if it's Ethereum (expensive, secure), a dedicated DA chain (Celestia, EigenDA), or an off-chain committee.
- Sub-step 2: Analyze proof costs. For ZK-Rollups, estimate the prover's computational cost and the verifier's on-chain gas cost for the proof verification contract.
- Sub-step 3: Test finality latency. Measure time from transaction submission to full finality, which differs for Optimistic (7-day challenge window) vs. ZK (immediate) rollups.
solidity// Example: Simplified interface for a ZK verifier contract interface IZkVerifier { function verifyProof( uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[2] memory input ) external view returns (bool); }
Tip: For high-frequency applications, ZK-Rollups with fast provers and low-latency DA are critical. For less time-sensitive, high-value apps, the security of Ethereum DA may be preferable.
2
Design for Native Account Abstraction and Interoperability
Implement smart accounts and plan for cross-chain and cross-rollup interactions.
Detailed Instructions
Future L2s will likely have native Account Abstraction (ERC-4337) at the protocol level, moving away from Externally Owned Accounts (EOAs). Design your dApp's user onboarding and transaction flows around smart contract wallets. Simultaneously, architect for a multi-L2 future where liquidity and users are fragmented.
- Sub-step 1: Integrate with the L2's AA entry point. Use the canonical
EntryPointcontract for bundling and paying gas in ERC-20 tokens via paymasters. - Sub-step 2: Implement cross-L2 messaging. Use the native bridge's message passing (e.g., Arbitrum's L1->L2 retryable tickets) or a third-party interoperability protocol (LayerZero, Hyperlane).
- Sub-step 3: Standardize contract interfaces. Use ERC-5164 for cross-chain execution or similar standards to ensure your contracts can receive calls and tokens from any connected chain.
solidity// Example: Minimal smart account capable of sponsored transactions via a paymaster contract MySmartWallet { function validateUserOp(UserOperation calldata userOp, bytes32 userOpHash, uint256 missingAccountFunds) external returns (uint256 validationData) { // ... signature validation logic if (missingAccountFunds > 0) { IPaymaster(msg.sender).postOp(PostOpMode.opSucceeded, userOp, missingAccountFunds); } } }
Tip: Assume users will have a single smart account identity across many L2s. Design your system to query and aggregate user state across these environments.
3
Optimize for the L2's Specific Execution Environment
Tailor contract logic and tooling to the unique VM, precompiles, and fee mechanisms.
Detailed Instructions
Each L2 has a distinct execution environment (EVM-compatible, SVM, MoveVM, WASM) with unique precompiles and gas metering. Ignoring these leads to inefficiency and high costs. Fee mechanisms also vary, with some L2s using a pure gas model and others implementing congestion fees or storage rent.
- Sub-step 1: Benchmark opcode costs. The gas cost for
SSTORE,CALL, and cryptographic operations likeECRECOVERcan differ drastically from Ethereum L1. Use the L2's fee documentation. - Sub-step 2: Leverage native precompiles. For example, zkSync Era offers precompiles for elliptic curve operations and keccak256 hashing that are far cheaper than in-contract computation.
- Sub-step 3: Adapt to storage models. Some L2s (Starknet) use a storage commitment model. Understand how writing to storage affects proof size and cost, not just immediate gas.
solidity// Example: Using a zkSync Era-specific precompile for efficient hash function hashWithZkSyncKeccak(bytes memory _data) internal view returns (bytes32) { bytes32 result; assembly { // Precompile address for keccak256 on zkSync Era let success := staticcall(gas(), 0x01, add(_data, 32), mload(_data), &result, 32) if iszero(success) { revert(0, 0) } } return result; }
Tip: Always run your test suite on the target L2 testnet. Gas profiling on a local Ethereum fork will give misleading results.
4
Plan for Decentralized Sequencer and Governance Risks
Understand and mitigate the centralization risks in the L2's sequencing and upgrade process.
Detailed Instructions
Most current L2s have a single, centralized sequencer controlled by the team. Future L2s promise decentralized sequencing via PoS or committee-based models. The upgrade mechanism for the L2's core contracts is a critical governance risk, often managed by a multi-sig or DAO.
- Sub-step 1: Scrutinize the sequencer's liveness and censorship. Check historical downtime and the protocol's mechanism for forced inclusion of transactions via L1 if the sequencer is offline.
- Sub-step 2: Review the security council and upgrade timelock. Identify who holds upgrade keys, the required threshold, and the delay (e.g., a 10-day timelock on the
L1Bridgecontract). - Sub-step 3: Model economic security. For PoS sequencer sets, analyze the staking token's distribution, slashing conditions, and the cost to attack the network.
solidity// Example: Querying a canonical bridge for a forced inclusion path interface IL1Bridge { function depositTransaction( address _to, uint256 _value, uint64 _gasLimit, bool _isCreation, bytes memory _data ) external payable; } // This function on L1 allows forcing a tx to be included on L2 if the sequencer censors.
Tip: Do not assume instant finality from the sequencer. Design your application to handle temporary sequencer failure and leverage L1 escape hatches for critical withdrawals.
5
Integrate Modular Services and Layer 3s
Prepare your application to leverage specialized L3s and external modular services.
Detailed Instructions
The future is modular, with L2s acting as a settlement layer for Layer 3s (L3s) or app-chains that offer hyper-scalability and customizability. Your dApp may need to deploy logic across multiple layers. External services like oracles and keepers must also be chosen for their L2 compatibility and latency.
- Sub-step 1: Map functionality to the appropriate layer. Use the base L2 for high-value settlement and finality. Deploy game loop logic or micro-transactions on a dedicated, low-cost L3 built atop it (e.g., a Starknet app-chain).
- Sub-step 2: Select L2-native oracle feeds. Use oracles like Chainlink that have low-latency, low-cost data feeds deployed directly on the target L2, not just bridged data from L1.
- Sub-step 3: Deploy contract automation. Use services like Gelato or Chainlink Automation that support your specific L2, ensuring they can pay gas and trigger functions reliably.
solidity// Example: A contract on an L3 checking a price from an L2-native oracle contract L3TradingApp { AggregatorV3Interface internal priceFeed; constructor(address _l2OracleAddress) { // Oracle address is on the parent L2, accessible via the L2->L3 messaging bridge priceFeed = AggregatorV3Interface(_l2OracleAddress); } function getLatestPrice() public view returns (int) { (,int price,,,) = priceFeed.latestRoundData(); return price; } }
Tip: Consider the trust assumptions and latency of cross-layer messages when designing a multi-layer application. The security of the L3 derives from its parent L2.
Frequently Asked Questions
The primary challenge is state fragmentation across different Layer 2 rollups. Each L2 maintains its own isolated state, making it difficult for a smart contract on one chain to directly read or trigger an action on another. This requires complex bridging protocols and interoperability standards. For instance, a lending protocol on Arbitrum cannot natively use an NFT on Optimism as collateral without a trusted bridge relaying the proof of ownership. Solutions like shared state proofs and universal messaging layers are in development but add latency and cost, often requiring 10-20 minute finality windows for secure cross-chain transactions.