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G2i Inc. | United States | $81k - $112k | |||
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Crossmint | Spain | $122k - $150k | |||
Animoca Brands Limited | Singapore, Singapore | $72k - $100k | |||
| Learn job-ready web3 skills on your schedule with 1-on-1 support & get a job, or your money back. | | by Metana Bootcamp Info | |||
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Mundy Buddy Publishing LLC. | United States | $72k - $112k |
This position is open to U.S.-based candidates only, applications from other regions will not be considered.
Contract Duration: Initial 2–3 month contract with the potential for long-term extension or full-time conversion based on performance and company fit.
Our client — an early-stage fintech startup — is developing a blockchain-based payment system designed to enable real-time, 24/7 movement of digital money across traditional finance and digital asset ecosystems. The company is building a new class of financial infrastructure that brings cash on chain through tokenization, powering payments for banks, digital asset exchanges, and the customers they serve.
We’re seeking a Lead Smart Contract Engineer to architect and implement secure, scalable smart contracts within a ZK Sync–based environment. You’ll help design and build the on-chain infrastructure that powers real-time tokenized payments and settlements — a critical foundation for next-generation financial systems.
About the Role
Reporting directly to the CTO, you’ll be responsible for the end-to-end design, development, and security of smart contract systems. This includes building core payment and settlement contracts, establishing best practices for testing and deployment, and collaborating with internal teams and external stakeholders to bridge on-chain infrastructure with traditional finance systems. This is a greenfield opportunity — you’ll be building everything from the ground up.
What You’ll Do
Architect and implement smart contracts for payment protocols, tokenization, and settlement on ZK Sync
Write production-ready Solidity code for core financial contracts, multi-signature wallets, and token standards
Conduct formal verification, invariant testing, and advanced security reviews to ensure contract safety
Use Foundry for testing, fuzzing, and deployment automation
Build TypeScript/Node.js integration services connecting contracts with backend systems (via WebSockets/webhooks)
Lead technical decision-making around gas optimization and ZK rollup implementation strategies
Establish internal standards for documentation, testing, and deployment
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Collaborate with stakeholders to align compliance requirements with decentralized design principles
Qualifications
5+ years of experience in smart contract development using Solidity and the EVM
Proven record deploying and managing production contracts exceeding $10M TVL
Deep understanding of smart contract security, vulnerabilities, and mitigation strategies
Hands-on experience with Foundry for testing, debugging, and CI/CD integration
Strong knowledge of ZK rollups, especially ZK Sync architecture
Experience building real-time systems (WebSockets, webhooks)
Expertise in DeFi protocols and token standards (ERC-20, ERC-721, ERC-4626)
Ability to work independently as the smart contract domain expert
Familiarity with formal verification tools and smart contract audits
What is ERC20 example?
ERC20 is a standard for fungible tokens on the Ethereum blockchain
Here is an example of an ERC20 token
Let's say we create a new ERC20 token called ABC Token with a total supply of 1,000,000 tokens
Each token will be divisible up to 18 decimal places
To implement the ERC20 standard, we will need to define several functions, including:
- balanceOf(address): Returns the token balance of a specific address.
- transfer(address to, uint256 value): Transfers tokens from the caller's address to the specified address.
- approve(address spender, uint256 value): Approves a specific address to spend a certain amount of tokens on behalf of the caller.
- allowance(address owner, address spender): Returns the amount of tokens approved by the owner that the spender can transfer.
- User1 owns 500,000 ABC Tokens.
- User2 wants to buy 100 ABC Tokens from User1.
- User1 approves User2 to spend up to 100 ABC Tokens on her behalf.
- User2 calls the transferFrom() function with User1's address, his own address, and the value of 100 tokens.
- The transferFrom() function deducts 100 tokens from User1's balance and adds them to User2's balance.