Building a decentralized app requires finding developers who understand both smart contract architecture and frontend integration—two very different skill sets that rarely coexist in one person. When vetting dApp developers, you need to know exactly what to ask for and what red flags signal inexperience or overconfidence.
Core Technical Skills to Verify
Smart Contract Development
Ask candidates to show you code samples in Solidity (Ethereum), Rust (Solana), or Move (Aptos), depending on which blockchain your project targets. Don't accept vague answers like "I know Solidity." Instead, probe their understanding of gas optimization, reentrancy vulnerabilities, and formal verification.
Request a portfolio dApp or GitHub repositories where they've written production contracts. Look for:
- Evidence of audit participation or external code reviews
- Use of libraries like OpenZeppelin for standard implementations
- Clear documentation of contract functions and state changes
Smart contract developers typically charge $80–$200+ per hour, or $15,000–$80,000+ for complete contract suites, depending on complexity.
Blockchain Selection Expertise
Different chains have vastly different development environments. A developer proficient in Ethereum's EVM ecosystem won't automatically translate to Solana's instruction-based model. Verify that your developer has shipped projects on the specific blockchain you're targeting, not just taken courses on it.
Questions to ask:
- Have you deployed contracts to mainnet on [your chain]?
- What are the unique constraints of [your chain] that affect your code?
- How do transaction finality and block times affect your architecture?
Frontend and Integration Skills
Web3 Integration Libraries
Your dApp's frontend communicates with smart contracts through libraries like ethers.js, web3.js, Anchor (Solana), or thirdweb. Verify developers can:
- Connect wallets (MetaMask, Phantom, Ledger, etc.) programmatically
- Call contract functions and handle transaction confirmations
- Parse and display blockchain data correctly
- Handle private keys and seed phrases securely (or delegate to hardware wallets)
Ask for a live dApp demo where they walk through a wallet connection and contract interaction. If they can't, they lack hands-on experience.
Security and Wallet Best Practices
Never hire developers who store private keys client-side or propose custom wallet solutions. Legitimate dApp developers integrate established wallets and use account abstraction patterns like ERC-4337 where needed.
Request evidence they understand:
- MetaMask security best practices
- Hardware wallet integration
- Signing messages versus transactions
- Rate limiting and transaction validation on the backend
Testing and Auditing Track Record
Production dApps need test coverage on testnet environments before mainnet deployment. Verify that candidates:
- Write automated tests for smart contracts (using Hardhat, Foundry, or similar)
- Use testnet faucets and staging environments
- Have experience with test transaction simulation and gas estimation
Ask if they've worked with auditors or security firms. Small projects may skip formal audits, but developers should at least understand what audits check for.
Proven Experience Markers
Look for developers who can demonstrate:
- Published contracts on Etherscan, Solscan, or equivalent block explorers (with documentation)
- GitHub contributions to Web3 projects, even if minor
- Community presence—active in Ethereum Research forums, GitHub discussions, or chain-specific Discord channels
- Previous client work—case studies or references from other dApp launches
- Continuous learning—awareness of protocol upgrades (Shanghai, Dencun, etc.) and new standards (ERC standards, token standards)
Project timelines vary widely: simple token contracts with basic UI might take 4–8 weeks; complex DeFi protocols with governance can take 6+ months.
Where to Start Vetting
Ask candidates for:
- A GitHub profile with relevant repositories (not empty accounts)
- Deployed contract addresses on testnet you can inspect
- Links to production dApps they've shipped
- References from previous clients
- Written answers to 2–3 technical questions specific to your project
Mercoly lets you compare and evaluate multiple blockchain developers in one place, making it easier to cross-reference their portfolios, rates, and past work before moving forward.
Frequently Asked Questions
Q: What's the difference between an Ethereum developer and a Solana developer? Ethereum developers write Solidity and typically use ethers.js; Solana developers use Rust and Anchor framework. They're not interchangeable—hire for your chain.
Q: How much should a production dApp cost? Simple token contracts with basic UI: $15,000–$50,000. Mid-range DeFi dApps: $50,000–$200,000. Complex protocols with governance: $200,000+. Costs scale with security requirements and audits.
Q: Should I hire one full-stack developer or separate smart contract and frontend specialists? For projects over $100,000, separate specialists often deliver better security and UI. For smaller projects, a skilled full-stack Web3 developer can work, but verify both sides of their portfolio.
Start by requesting portfolios and testnet contract examples from candidates—this filters out inexperienced applicants immediately.