A few years ago a blockchain developer could get hired on the strength of a token contract and some time in Remix. That is no longer enough. Contracts now sit on layer-2 networks, call bridges and other protocols, serve smart accounts, and get read by auditors and attackers within hours of deployment. AI assistants also produce plausible Solidity on demand, so writing contract code has become the easy part. The hard part is knowing what that code does under pressure, proving it with tests, and designing controls that let a team fix a mistake without handing anyone the keys to user funds.
This guide sets out the blockchain developer skills worth paying for in 2026, what good looks like for each, and a practical way to check it while hiring. If you still need to write the role itself, our blockchain developer job description has a template and the levels.
Core technical skills for a blockchain developer
Solidity, with a clear model of the EVM underneath
Good Solidity developers know what their code compiles into. They understand how call, delegatecall and staticcall differ, what happens to state when an external call reverts, and why unchecked arithmetic is a deliberate decision rather than a habit.
How to check it: show a short function that forwards a call to another contract and ask the candidate to explain whose storage changes and who msg.sender is at each step.
Tests that describe what the contract must never do
Strong developers treat tests as a specification. In Foundry or Hardhat they cover each path, but they also state properties that must hold whatever happens, such as total deposits never exceeding the contract balance, and let fuzzing try to break them. They know full line coverage says little about whether dangerous combinations have been tried.
How to check it: hand over a small contract whose tests reach every line but miss an edge case, and ask what the tests fail to prove. A good candidate names the missing property and writes a test for it.
Threat modelling before code review
Security starts before anyone opens a file. A capable developer can list who is able to move funds, change parameters or pause the system, what an attacker gains from each route, and which outside inputs, such as oracle prices or signed messages, the contract trusts. Signature replay, front-running and flash-loan price moves belong in that picture alongside reentrancy.
How to check it: describe a simple staking vault in a paragraph and give the candidate fifteen minutes to write its threat model. Look for actors, assets and trust assumptions, not a list of vulnerability names.
Upgrade, admin and key design
Many incidents begin with privileged functions. Good developers understand UUPS and transparent proxies, keep storage layouts compatible between versions, and put admin powers behind a multisig such as Safe with a timelock, so users can see a change coming.
How to check it: share a diff between two versions of an upgradeable contract in which a new variable has been inserted above existing ones, and ask whether it is safe to deploy. The strongest candidates spot the storage collision and suggest how to catch it automatically.
Integrating with tokens and protocols that misbehave
Real contracts hold tokens that charge a fee on transfer, rebase balances or return nothing from transfer. Developers who have shipped use OpenZeppelin’s SafeERC20, measure balances before and after a transfer when it matters, and read the code of any protocol they plug into rather than trusting its documentation.
How to check it: ask how their own contract would cope if a user deposited a fee-on-transfer token.
Off-chain services: indexing, RPC and transactions
Every dApp depends on code that reads events, sends transactions and recovers when an RPC node fails. Good developers use Viem or Ethers.js comfortably, build indexers that cope with chain reorganisations, manage nonces for backend wallets, and treat dropped or replaced transactions as normal states.
How to check it: ask what their indexer does when a block it has already processed is replaced.
Rust and the account model, for Solana
Solana programs, usually written in Rust with the Anchor framework, keep state in accounts passed into each instruction, so the developer must check signers, owners and account relationships explicitly. Someone moving from Solidity needs to show they have made that shift, not just learned Rust syntax.
How to check it: ask which checks they add to an instruction that withdraws funds, and what goes wrong if the owner check is missing.
Hyperledger Fabric and permissioned ledgers
Enterprise projects in trade finance or document verification often run on Hyperledger Fabric, where the work is closer to distributed backend engineering. Chaincode is commonly written in Go, Java or JavaScript, and the key decisions concern endorsement policies, channels and private data shared between organisations.
How to check it: describe a consortium of a bank, an exporter and a shipping line, and ask how they would set the endorsement policy and what each member should see.
Working skills that separate good from average
- Writing for the reviewer. Good developers leave NatSpec comments on public functions, a short design note and a list of known risks before an audit begins, so auditors spend their time on real issues rather than reconstructing intent.
- Thinking like someone with money at stake. The best developers reason about incentives. They ask what a large holder or a liquidator would do with a feature, and notice when an innocent parameter change makes an attack profitable.
- Explaining risk to people who are not engineers. When a product lead wants a feature live this week, the developer has to explain why a timelock or a second review matters in terms of what users could lose.
- Owning the contract after launch. Strong candidates set up alerts on critical functions, rehearse how to pause a contract, and know who must sign what during an incident.
Skills that matter more in 2026, and skills that matter less
Matter more
- Reviewing generated code. AI assistants write Solidity that compiles and looks idiomatic. The developer’s value now lies in catching the subtle mistakes in it, which makes careful reading and property-based testing worth more than typing speed.
- Fuzzing and invariant testing as routine. Foundry’s built-in fuzzer, Echidna and Medusa have moved property-based testing from the auditor’s desk into normal development.
- Layer-2 and cross-chain awareness. Much activity now happens on rollups and many products span several chains, so developers need to understand bridge trust assumptions and differences between EVM-compatible networks.
- Smart accounts. Account abstraction through ERC-4337, and EIP-7702 for ordinary wallets, changes how users sign, how gas is paid and what a contract can assume about its caller.
- Compliance-aware design. Tokenised assets and regulated payments bring allowlists, transfer restrictions and clear admin controls into contract design.
Matter less
- Extreme gas optimisation. Gas is far cheaper on layer-2 networks, so inline assembly that saves a little gas at the cost of readability is harder to justify.
- The older toolchain. Truffle and Ganache have been retired by their maintainers. A candidate who has not moved to Foundry or Hardhat has probably not shipped recently.
- Standard components written from scratch. Hand-rolled ERC-20 and ERC-721 contracts were once a portfolio staple. Audited libraries turned that into a liability.
Blockchain developer skills matrix by level
| Skill area | Junior | Mid-level | Senior |
|---|---|---|---|
| Solidity and EVM | Writes clear contracts from a spec using audited libraries | Understands call types, storage and failure behaviour | Sets coding standards, reviews low-level code |
| Testing | Unit tests for main paths | Fuzz, invariant and forked tests | Defines the properties the system must keep |
| Security | Knows common vulnerability classes | Threat models own features, fixes audit findings | Owns the security model and audit planning |
| Upgrades and admin | Follows the team’s proxy pattern | Ships upgrades safely, checks storage layout | Designs multisig, timelock and pause controls |
| Off-chain integration | Scripts and simple reads | Builds indexers and reliable transaction services | Designs the on-chain and off-chain architecture |
| Communication | Asks for review early | Writes design notes and audit documentation | Explains risk to leadership and partners |
How to assess blockchain developer skills in a hiring process
A practical process tests reading and reasoning more than recall. Keep each exercise short and close to your own codebase.
- A pull request review. Prepare a realistic pull request with one serious issue, a couple of minor ones and some harmless style changes, and ask for review comments. You learn how the candidate prioritises and how they phrase criticism.
- A paired debugging session. Give them a failing Foundry test and thirty minutes. Watch whether they read the trace before changing code.
- A release walkthrough. Ask how they would ship a new version of a live contract holding user deposits, from code freeze to the day after launch. Good answers cover review, the upgrade path, who signs and how users are told.
- A look at commit history. In a public repository, contracts that appeared in one commit with no tests and no iteration often came from somewhere else.
Red flags on a CV include a long list of chains with no project behind each, portfolios made only of course projects such as a basic NFT mint, “audited” contracts with no named reviewer or findings, and repositories with no test folder.
If you would rather meet candidates already screened this way, you can hire blockchain developers in India through Zilo AI on contract, contract-to-hire or permanent terms. We also staff the backend, front end and QA engineers who build around the chain through our IT hiring services.
Frequently asked questions
Can a strong backend developer become a good blockchain developer?
Often, yes. Backend engineers bring testing habits and an understanding of distributed systems. What they need to add is the mindset that deployed code is public, hard to change and constantly probed. Look for someone who has already built and tested contracts on their own.
How deep does a blockchain developer’s cryptography knowledge need to be?
Most application developers need a working grasp of hashing, digital signatures and signature replay, so they can use standards such as EIP-712 correctly. Zero-knowledge circuits and new cryptographic schemes are a separate specialism to hire for explicitly.
Are audit contest results a useful hiring signal?
They can be. Valid findings on platforms such as Code4rena, Sherlock or Cantina show someone can find real issues in unfamiliar code. Ask the candidate to walk through one finding, then check separately that they can design and ship contracts of their own.
Has AI-assisted coding changed what to test for in interviews?
Yes. Since code can be generated quickly, writing a contract from scratch tells you less than it used to. Exercises built on reading and reviewing, such as a flawed test suite or an unsafe upgrade, now say more about how someone will perform.
If you are building a team for smart contracts, a dApp or a permissioned ledger, Zilo AI can shortlist blockchain developers screened on tested, shipped work. Talk to our team about your chain, your stack and what your contracts will control.