How to Plan a Migration from Layer 1 to a ZK Rollup

Migrating a decentralized application from a Layer 1 (L1) like Ethereum mainnet to a ZK Rollup such as zkSync Era, Starknet, or Polygon zkEVM is a major architectural shift. The primary drivers are cost reduction—transaction fees can be 10-100x cheaper—and scalability, enabling higher throughput without congesting the base layer. This move is not a simple redeployment; it requires a strategic plan that addresses contract logic, state management, user onboarding, and security assumptions. A successful migration balances immediate user benefits with long-term protocol resilience.

The planning phase begins with a comprehensive audit of your current L1 architecture. You must inventory all smart contracts, their dependencies, and the state variables they manage. Pay special attention to contracts that interact with L1-native services like oracles (e.g., Chainlink), bridges, or governance modules. For example, a DeFi protocol's price feed integration will need a new strategy, as the oracle may publish directly to the rollup or require a custom relay. This audit will define the scope of the migration, identifying which components can be redeployed with minimal changes and which require a full redesign for the rollup's environment.

Next, you must select a ZK Rollup stack and understand its specific constraints. While all ZK Rollups share core principles, their virtual machines differ: zkSync Era uses a custom zkEVM, Starknet uses Cairo, and Polygon zkEVM aims for bytecode-level EVM equivalence. This choice dictates your development tools, language (Solidity, Vyper, Cairo), and the availability of pre-compiled system contracts. You should prototype a core piece of logic on the target rollup's testnet to validate gas costs, confirm opcode compatibility, and test interactions with the rollup's native bridge for asset transfers from L1.

A critical technical step is designing the state migration and data availability strategy. You cannot simply copy storage slots from L1 to L2. Common patterns include: a gradual migration using a bridge that locks L1 assets and mints equivalents on L2; a snapshot-and-claim model where user balances are recorded on L1 and claimable on the new L2 contract; or a dual-operation phase where the system runs on both chains temporarily. Each approach has trade-offs in complexity, user experience, and security. The chosen method must be clearly communicated to users, with robust front-end support for the transition.

Finally, plan for post-migration operations and security. This includes setting up new monitoring for L2 transactions, configuring multisig wallets for rollup-specific admin functions, and understanding the escape hatch or force-withdrawal mechanisms in case the rollup sequencer fails. You should also budget for ongoing L1 costs, as rollups periodically post compressed transaction data and validity proofs to Ethereum, which your protocol may help subsidize. A well-planned migration turns scalability gains into a sustainable advantage, positioning your application for the next wave of user adoption on Layer 2.

Migrating from a Layer 1 (L1) like Ethereum Mainnet to a ZK Rollup is a major architectural shift, not a simple redeployment. The first prerequisite is a deep technical audit of your existing smart contracts. You must assess their compatibility with the rollup's EVM-equivalent or EVM-compatible environment (e.g., zkSync Era, Starknet, Polygon zkEVM). Key considerations include opcode support, precompiles, gas metering differences, and contract size limits. This audit will reveal if contracts require refactoring or if certain functionalities need alternative implementations.

A critical strategic prerequisite is defining your data availability and settlement model. ZK Rollups post compressed transaction data and validity proofs to an L1. You must decide if your rollup will use the base L1 (Ethereum) for maximum security or an alternative Data Availability (DA) layer like Celestia or EigenDA for lower costs. This choice directly impacts trust assumptions, finality time, and operational expenses. Furthermore, understand the withdrawal delay mechanism; users typically wait for a challenge period when moving assets back to L1, which affects UX design.

You must establish a robust development and testing pipeline. This involves setting up a local development node for your target rollup (e.g., using hardhat-zksync or starknet-devnet) and integrating it with your CI/CD. Comprehensive testing is non-negotiable: you need unit tests, integration tests simulating cross-chain messaging, and stress tests for the new gas economics. Budget significant time for testing on public testnets before mainnet deployment, as rollup environments can have subtle differences in transaction ordering and block gas limits.

Plan your governance and upgradeability path. Rollup smart contracts, especially the core bridge and sequencer, are often upgradeable via multisigs or DAOs. You need a clear, secure plan for managing upgrade keys and emergency pauses. If your protocol has its own governance token, decide how voting will interact with the new layer—will governance remain on L1, migrate to L2, or operate cross-chain? Tools like OpenZeppelin Defender or Safe{Wallet} are essential for managing this secure operations workflow.

Finally, prepare for the operational shift. This includes monitoring new metrics like L1 data posting costs, proof generation latency, and sequencer health. You'll need RPC endpoints from providers like Alchemy or Infura that support your rollup. Educate your community about the new user experience: different wallet setups (e.g., injecting the network), bridging assets, and explaining potential delays. A successful migration is as much about preparing your users and ops team as it is about the technical deployment.

The first step is a comprehensive technical audit of your existing smart contracts and application logic. ZK rollups, like Starknet, zkSync Era, or Polygon zkEVM, operate in a different execution environment with unique constraints. You must assess compatibility with the rollup's virtual machine (e.g., Cairo VM, zkEVM), gas opcode behavior, and block gas limits. Tools like static analyzers and the rollup's local development net are essential for identifying incompatible patterns, such as reliance on specific L1 block hashes or opcodes not yet supported in the ZK circuit.

Concurrently, perform an economic and user impact analysis. Calculate the projected cost savings from reduced L1 gas fees versus the new fee structure of the rollup, which includes prover costs and L1 data availability fees. Model the impact on your users: will they need new wallets? How will asset bridging work? You must also evaluate the security model shift: your application's security will now depend on the cryptographic correctness of the rollup's validity proofs and the liveness of its data availability layer on Ethereum L1.

Based on the audit, you must choose a migration strategy. A full migration rewrites and redeploys all contracts on the rollup. A partial migration or L2-centric design keeps core settlement on L1 while moving high-throughput operations (like perp trading or gaming logic) to L2. For existing tokens, decide between using the rollup's native bridging infrastructure or deploying a fresh token with a snapshot-based airdrop. Each choice has profound implications for user onboarding, liquidity fragmentation, and protocol governance.

Finally, create a detailed rollup provider evaluation matrix. Compare key metrics across contenders: time-to-finality, proven throughput (TPS), cost structure for developers and users, programming language (Solidity vs. Cairo vs. Zinc), ecosystem size, and the roadmap for decentralization of the sequencer and prover networks. This due diligence ensures the chosen stack aligns with your application's technical needs and long-term decentralization goals.

The first critical decision is your state model. A ZK Rollup can adopt an account-based model (like Ethereum) or a UTXO-based model (like Zcash). The choice dictates how you manage user balances and smart contract interactions. For a DeFi application with complex composability, an account model is often necessary. You must define the exact structure of your state tree (e.g., a Sparse Merkle Tree) and the logic for state transitions, which will be encoded into your circuit constraints.

Next, you must select a data availability (DA) layer. While Ethereum is the canonical choice, posting all transaction data as calldata is expensive. Alternatives include using EIP-4844 blobs for cheaper data, a validium with an off-chain DA committee, or a volition that lets users choose per-transaction. Your DA choice is a direct trade-off between security, cost, and decentralization. For a high-throughput gaming rollup, a validium might be suitable, while a decentralized exchange typically requires the highest security of Ethereum DA.

The proving system is the engine of your ZK Rollup. You'll choose between SNARKs (e.g., Groth16, PLONK) and STARKs. SNARKs require a trusted setup but have smaller proof sizes and faster verification. STARKs are trustless but generate larger proofs. Most existing rollups like zkSync and Polygon zkEVM use SNARK variants. You must integrate a proving backend (like Halo2, Plonky2, or RISC Zero) and design circuits that efficiently verify your application's execution.

Your sequencer design handles transaction ordering and block production. Will you run a single, permissioned sequencer for simplicity, or design a decentralized sequencer set? The sequencer batches transactions, executes them to generate a new state root, and submits the batch data and a validity proof to the L1. It must handle tasks like transaction fee collection in the rollup's native gas token and managing reorgs. The architecture must ensure the sequencer cannot censor transactions without detection.

Finally, you need to plan the bridge and messaging layer between L1 and your rollup. This includes a bridge contract on Ethereum to verify ZK proofs and hold locked assets, and a mechanism for cross-chain messages. For arbitrary message passing, you might implement a system like LayerZero or Hyperlane on your rollup, or build a custom light client verifier. Users must be able to securely deposit assets from L1 and withdraw them back, a process that relies entirely on the security of your proof system.

The core of a migration is a dedicated bridge contract deployed on both the Layer 1 (L1) source chain and the ZK rollup (L2) destination. On L1, this contract holds the original assets (e.g., ERC-20 tokens, NFTs) that users lock or burn. It emits an event upon deposit. The rollup's sequencer picks up this event, and the ZK proof system verifies its inclusion in an L1 block, allowing the L2 bridge contract to mint an equivalent representation of the asset. This process, known as a canonical bridge, ensures a 1:1, verifiably-backed asset supply on L2. For custom tokens, you must deploy a mirrored token contract on L2 with matching metadata.

User experience is critical. You must provide a front-end migration portal that interacts with these bridge contracts. The portal should guide users through the approval and deposit steps, display clear transaction status (from L1 confirmation to L2 finality), and show the new L2 balance. For a smoother transition, consider implementing a gas sponsorship mechanism on L1, where the project pays the gas fees for user deposits, removing a major barrier. Communication must detail the migration window, the immutable nature of locking assets, and the security model of the ZK bridge. Transparency about withdrawal delays (the time to challenge a fraud proof or generate a validity proof) is essential for trust.

Beyond simple transfers, plan for contract state migration. If your L1 dApp has complex state (e.g., staking positions, governance votes), you'll need a migration module to snapshot this data and replicate it on L2. This often involves a multi-step process: 1) pausing L1 operations, 2) taking a verifiable state root snapshot, 3) publishing the snapshot and a Merkle proof on-chain, and 4) allowing users to claim their migrated state on L2 using that proof. Tools like Hardhat or Foundry scripts are indispensable for automating bulk state snapshots and generating the necessary proof data.

Post-migration, your infrastructure must support the new L2 environment. Update your indexers, oracles, and backend services to read from the rollup's RPC endpoint. Monitor the bridge contract for unusual activity and set up alerts. Finally, establish a clear post-migration support channel to assist users with issues. A successful migration is not just a technical lift-and-shift; it's a coordinated effort that balances smart contract security, user experience design, and transparent communication to move your community and its assets onto a more scalable foundation.

A phased deployment is critical for mitigating risk and ensuring a smooth user transition. The core strategy involves deploying your application's smart contracts to the ZK rollup first, while keeping the canonical version and user funds on the original L1. This creates a one-way bridge where users can voluntarily migrate assets and interact with the new rollup-based application. During this phase, the L1 contract acts as the single source of truth, with the rollup state being a verifiable derivative. Tools like Foundry or Hardhat are essential for deploying and verifying your contract suite on the new chain, ensuring bytecode matches your L1 deployment exactly where logic is shared.

Begin with a canary launch or beta program for a limited set of users. This involves whitelisting a small cohort—such as community members or power users—to interact with the rollup deployment. Monitor key metrics: transaction success rates, GAS costs on the rollup versus L1, sequencer latency, and bridge finality times. This real-world data is invaluable for stress-testing your integration and catching edge cases not present in testnets. It also builds early community trust and generates organic feedback. Ensure you have robust monitoring for the rollup's sequencer and data availability layer to preemptively identify any network-level issues.

The official go-live involves removing access restrictions and initiating a coordinated migration campaign. Communicate a clear timeline to users, detailing the benefits (lower fees, faster transactions) and the migration process. Provide user-friendly front-end interfaces for bridging assets, potentially using SDKs from the rollup team (like StarkNet's starknet.js or zkSync's zksync-web3). Consider implementing liquidity incentives to bootstrap the new rollup deployment, but ensure these are sustainable. Crucially, maintain the L1 application in a read-only or deprecated state, redirecting all new activity to the rollup URL. Your go-live checklist should include final security audits, disaster recovery plans, and a rollback procedure defined in case of critical failures.

Your migration plan should follow a phased approach. Start with a comprehensive audit of your existing L1 smart contracts, focusing on state variables, storage layout, and dependencies on L1-specific opcodes like block.number or block.coinbase. Tools like the Foundry testing framework and Slither static analyzer are essential here. Next, establish a dedicated testnet environment on your target rollup (e.g., zkSync Era Sepolia, Starknet Goerli) to deploy and rigorously test your adapted contracts.

The core technical phase involves contract adaptation. You will need to modify contracts to be compatible with the rollup's virtual machine (e.g., zkEVM, Cairo VM). This often means replacing native L1 randomness oracles with the rollup's verifiable RNG, adapting gas estimation logic, and ensuring any off-chain components (like keepers) can interact with the new RPC endpoint. For critical state transitions, you may need to write circuit logic or leverage the rollup's SDK for custom proof generation, which requires specialized cryptographic engineering.

A staged production rollout is critical for risk mitigation. Begin by migrating non-critical, ancillary contracts to validate the toolchain and infrastructure. Use a canary deployment for the main protocol: launch the new rollup version with a limited asset cap or user group, running it in parallel with the L1 version. Employ a bridging facade contract on L1 that allows users to permissionlessly port their state to the new rollup address. Monitor key metrics like transaction finality time, proof generation cost, and RPC latency during this period.

Post-migration, your operational focus shifts. You must monitor sequencer health and have contingency plans for potential downtimes, which affect transaction inclusion. Understanding the data availability layer of your rollup is crucial for security; know where the transaction data is published (e.g., Ethereum calldata, Celestia) and the implications. Budget for ongoing proof submission costs on L1, which are your primary operational expense, and consider implementing gas abstraction or paymaster systems to improve user experience.

Finally, engage with the rollup's ecosystem. Explore native features you couldn't access on L1, such as account abstraction for session keys, shared liquidity pools, or interoperable state proofs with other apps on the same rollup. The migration is not just a lift-and-shift; it's an opportunity to rebuild with a more scalable and integrated architecture. Continue iterating based on the new performance baseline and user feedback from the faster, cheaper chain.