How to hire a blockchain developer: skills, interview questions and costs
Hiring for blockchain work carries more risk than most software roles, because a mistake in a deployed contract can be expensive and hard to undo. This guide covers what blockchain developers build, the skills to test, questions to ask, what affects the price and how to start safely. For the off-chain side of your product, also see our back-end developers.
What a blockchain developer works on
Most blockchain projects have two halves. On-chain, smart contracts hold the rules: who owns what, how payments move, what a token can do. Off-chain, a normal app gives people a way to use it: a website, wallet connections, an indexer that reads chain data and an API for the rest of your systems. Some developers specialize in contracts, others build across both halves, so be clear about which you need.
The ecosystem matters too. Ethereum and compatible chains use Solidity; Solana uses Rust; permissioned business networks such as Hyperledger Fabric use Go, JavaScript or Java. A developer strong in one is not automatically strong in another.
Skills to test
- Contract language: Solidity or Rust, written clearly with tests for every function.
- Security thinking: reentrancy, access control, front-running and oracle manipulation, and how to prevent them.
- Standards and libraries: ERC-20, ERC-721, ERC-1155 and audited OpenZeppelin code instead of home-made versions.
- Upgrades and keys: when to use upgradeable contracts, and how admin keys are protected with multi-signature wallets.
- Testing: unit and fuzz tests with Foundry or Hardhat, and a local fork of the chain for realistic tests.
- Product sense: wallets, gas costs and what users see when a transaction fails.
Questions worth asking
- Walk me through how a reentrancy attack works and how your code prevents it.
- How would you make this contract upgradeable, and what risks does that add?
- Who should hold the admin keys for our contracts, and how?
- A transaction fails for users at busy times. What do you check?
- Tell me about an audit finding on your code and how you fixed it.
Strong candidates answer with specifics, mention tests and tools they use, and are happy to say when a feature should not be on-chain at all.
Example job post
Keep it concrete: “We are hiring a blockchain developer to build and maintain the smart contracts behind our payments product on an EVM chain. You will write Solidity with OpenZeppelin, test with Foundry, prepare code for an external audit and connect the contracts to our TypeScript back end. Must have: deployed Solidity contracts holding real value, testing discipline. Nice to have: stablecoin payments and The Graph.” You can adapt our software engineer job description template for the longer version.
What affects the cost
Experience with contracts that have held real money is the biggest factor, followed by the ecosystem and the depth of security knowledge. Location changes the price as with any remote hire, with the US and Western Europe at the top of the range. Budget separately for an outside audit before any launch that holds user funds. At DigiWorks, the developer’s pay and our fee are shown as separate amounts.
Choosing the right level
A junior blockchain developer can help with tests, scripts and front-end wallet work, but should not be the only person writing contracts that hold money. A mid-level developer can build features to an agreed design with review. For your first contracts, an upgrade plan or anything handling user funds, choose a senior who has taken contracts through audits and live launches before, and who can explain the trade-offs to non-technical founders in plain words.
Start with a paid task
Give your final one or two candidates a short paid task: a small contract with clear rules, full tests and a written note on how it could be attacked. Keep it to a few hours and give everyone the same brief. The quality of the tests and the security note will tell you more than the contract itself.
Freelance or dedicated
Freelance help suits a single contract or integration with a fixed end. A product that keeps growing benefits from a developer who stays, because they know your contracts, keys and history, and they are around when something needs a careful upgrade.
The first three months
In week one, share the repositories, the test setup and the deployment process, and agree who holds which keys. In the first month, the developer should ship a reviewed change to testnet and improve test coverage. By the third month, they should own a part of the system, review others’ contract code and plan the next audit with you.
Mistakes to avoid
- Deploying contracts that hold real value without tests and an outside review.
- Keeping admin keys on one person’s laptop instead of a multi-signature wallet.
- Writing your own versions of standard tokens instead of using audited libraries.
- Putting things on-chain that would work better, and cheaper, in a normal database.
Building a wider remote engineering team? Read our remote software engineering hiring playbook.