How to hire a smart contract developer: skills, questions and costs
Once a smart contract is live, anyone can call it, and mistakes can cost a lot and are often impossible to reverse. That makes hiring for this role different from most software jobs. Below you will find the work itself, interview checks, cost factors and a safe way to onboard a new developer. If you need help with the wider product, such as wallets, indexers and the web app, see our blockchain developers and back-end developers.
What the role covers
A smart contract developer writes the code that runs on chain: token rules, vault accounting, auctions, governance votes, escrow and similar logic. On Ethereum and EVM networks that code is usually Solidity; on Solana it is Rust. Day to day, much of the job is not writing new functions but testing, reviewing, measuring gas and documenting how the system should behave, so that auditors and other engineers can check it.
Skills to check
- Solidity in depth: storage layout, visibility, events, custom errors and how calls between contracts behave.
- Testing: unit tests plus fuzz and invariant tests in Foundry, or a solid Hardhat setup.
- Security thinking: reentrancy, rounding, signature replay, front-running and unsafe admin powers.
- Standard libraries: knowing when to use OpenZeppelin Contracts instead of writing code from scratch.
- Upgrades: proxy patterns, storage collisions and safe initializers.
- Operations: deploy scripts, source verification, multisig wallets and monitoring after launch.
Interview questions that reveal experience
- Walk me through a contract you deployed. What would you change about it today?
- How do you prevent reentrancy, and where can it still sneak in?
- Here is a short function. Where can the maths round in the attacker’s favour?
- If this contract had to become upgradeable, which pattern would you pick and who would hold the upgrade rights?
- Which audit finding against your own code taught you the most?
Look for answers grounded in their own projects and honest about trade-offs. Be careful with anyone who dismisses audits or promises that their code cannot be hacked.
A sample job post
An example: “Our team needs a smart contract engineer to own the Solidity code of our protocol on an EVM layer 2. The role covers vault and reward logic, Foundry fuzz and invariant tests, audit preparation and our deploy scripts. You will pair with our back-end engineer and report to the product lead. Required: deployed Solidity in production and strong testing habits. Nice to have: proxy upgrades, Vyper or Rust.” A longer template is in our software engineer job description guide.
Cost factors
Seniority matters most. Someone who has shipped contracts that hold real value, worked through audits and handled incidents is worth more than a developer who has only built test projects. Breadth matters too: cross-chain work, complex maths or Rust on Solana narrow the pool. Location and hours play their usual part. At DigiWorks, you see the salary and our fee as separate numbers.
Picking the right level
Juniors are productive on narrow, well-specified contracts when a senior checks each pull request. Mid-level engineers can take a full module, tests included. For a sole contract engineer, or for code that will custody user funds, look for a senior who has already worked through audits and can explain risks in plain language to the rest of the team.
Testing on a fork
Good developers test against a local copy of the real network. A fork lets them call the actual tokens, price feeds and protocols your contracts depend on, without spending real money. Ask candidates how they use forks, how they pin a block number for repeatable tests and how they simulate a deployment before it happens.
Audits and bug bounties
An external audit lowers risk; it does not remove it. Plan time for it in your roadmap, freeze the code you send, and expect a round of fixes afterwards. Your developer should prepare a short spec, a threat model and clean tests before the audit starts. After launch, many teams add a bug bounty so outside researchers can report problems responsibly.
A paid trial
Ask each finalist to complete one identical, paid exercise: for example, a small escrow contract with tests, or a review of an existing contract with a written list of issues. Read the reasoning as carefully as the code. Clear notes about risks and assumptions are a good sign.
An onboarding plan
Week one: repository access, specs, deploy history and an agreed review process. Month one: the developer owns one contract and its tests on a testnet. Month three: they plan upgrades, lead reviews and prepare material for the next audit.
Mistakes to avoid
- Leaving admin rights with a single private key rather than a multisig.
- Deploying code that has not been fuzz tested or reviewed by a second person.
- Writing custom token or access control code when a standard, reviewed version exists.
- Treating the audit report as the end of security work rather than one step in it.
For hiring across your whole engineering team, our guide to hiring remote engineers goes into more detail.