Ethereum development in 2026

Describe the Ethereum Virtual Machine (EVM) execution environment, including the roles of memory, storage, and the stack.

Explain the transaction lifecycle, from creation and signing to inclusion in a block.

Analyze the factors determining transaction cost (gas) and the fee market mechanism (EIP-1559).

Differentiate between Externally Owned Accounts (EOAs) and Smart Contract Accounts.

Set up a Hardhat development environment with TypeScript configuration.

Configure Foundry for fast, Solidity-native testing and deployment workflows.

Compare the testing philosophies and workflows of Foundry (Solidity-scripted) and Hardhat (JavaScript/TypeScript-scripted).

Set up local blockchain nodes using Anvil or Hardhat Network with mainnet forking capabilities.

Write unit tests for a contract's happy path, covering state changes and return values.

Write tests for failure conditions, including expected reverts with custom errors.

Write tests to verify correct event emission and parameter values.

Implement fuzz testing with Foundry to discover edge cases in contract logic.

Write integration tests for multi-contract interactions within a single protocol.

Perform test coverage analysis to ensure comprehensive test suites.

Implement custom errors to replace require/revert strings for gas optimization and improved developer experience.

Apply the Checks-Effects-Interactions pattern to prevent reentrancy attacks.

Audit contracts for reentrancy vulnerabilities using static analysis (Slither) and manual review.

Implement access control using OpenZeppelin's AccessControl and Ownable patterns, and audit for common flaws.

Identify and prevent arithmetic issues (overflow/underflow), particularly when using unchecked blocks for gas optimization.

Use events with indexed parameters for efficient off-chain data querying.

Compare different upgradeability patterns (e.g., Transparent vs. UUPS) and their trade-offs.

Implement an upgradeable contract using the UUPS proxy pattern.

Implement an ERC-20 token with mint, burn, and pausable functionality.

Add permit functionality (ERC-2612) to an ERC-20 token for gasless approvals.

Implement the core swap logic of an Automated Market Maker (AMM) using the constant product formula (x * y = k).

Build a staking contract for an ERC-20 token with a time-based reward distribution mechanism.

Implement core lending pool functions for depositing collateral and borrowing assets.

Integrate a price oracle (e.g., Chainlink) to calculate an account's collateralization ratio.

Implement the liquidation logic to repay underwater debt and seize collateral.

Architect the data flow for a DeFi front-end, handling asynchronous state, transaction confirmations, and potential chain reorganizations.

Build an ERC-721 NFT contract with metadata URI management.

Implement an ERC-1155 multi-token contract for combined fungible and non-fungible assets.

Integrate decentralized storage (e.g., IPFS) for NFT metadata, managing on-chain URIs and off-chain asset retrieval.

Implement an NFT mint with an allowlist using Merkle proofs.

Implement on-chain royalty mechanisms using the ERC-2981 standard.

Build the smart contract logic for a simple NFT marketplace supporting fixed-price listings and purchases.

Extend the marketplace contract to support a basic auction system, including placing bids and settling the auction.

Implement a dynamic NFT that changes its metadata based on on-chain state or external events.

Deploy and verify a contract to an Ethereum Layer 2 network (e.g., Arbitrum, Optimism).

Describe the architectures and security trade-offs of different cross-chain communication patterns (e.g., native bridges, third-party protocols).

Implement a simple contract on a source chain that sends a message using a generic messaging protocol (e.g., LayerZero, CCIP).

Implement a corresponding contract on a destination chain that receives and processes the message.

Write a script to deploy and test the end-to-end cross-chain communication flow between two testnets.

Apply gas optimization techniques using storage packing and efficient use of calldata.

Rewrite a Solidity function using a Yul assembly block to reduce gas costs for complex operations.

Author a reusable deployment script (e.g., using Hardhat-deploy) for multiple networks.

Integrate a UUPS proxy pattern into a deployment script to manage contract upgrades.

Set up a monitoring service (e.g., Tenderly, OpenZeppelin Defender) to observe a deployed contract.

Configure custom alerts for critical contract events and function failures.

Implement gasless transactions using a relayer-based meta-transaction pattern (EIP-2771).

Build a gasless transaction flow using Account Abstraction (ERC-4337) with a Paymaster.

Compare relayer-based meta-transactions (EIP-2771) with native account abstraction (ERC-4337) for enabling gasless user experiences.

Describe the roles of the Bundler, EntryPoint, and Paymaster in the ERC-4337 ecosystem.