Zeljko K.

I architect and build dApps, protocols, and fintech products on EVM, Solana, and Stellar. The work runs from system design through smart contracts, APIs, and the user-facing application. That includes blockchain-native fintech: payments, wallets, and on-chain financial products. ✅ Solidity ✅ Smart contracts ✅ Ethereum ✅ Rust ✅ Solana ✅ DeFi ✅ Fintech ✅ KYC & KYB ✅ Web3 ✅ EVM ✅ Anchor ✅ Foundry ✅ OpenZeppelin ✅ ERC-20 ✅ ERC-721 ✅ SPL ✅ NFT ✅ ethers.js ✅ Crypto wallets ✅ TypeScript ✅ React.js ✅ Next.js ✅ Node.js ✅ Fastify ✅ PostgreSQL ✅ Python ✅ API development ✅ Payment gateway integrations ✅ Base ✅ Binance/BSC/BNB ✅ Arbitrum ✅ Optimism ✅ Robinhood ✅ Arc ✅ Unichain ✅ Polygon ✅ Avalanche Solidity with Foundry and OpenZeppelin. Solana programs in Rust with Anchor. Token and NFT contracts: ERC-20, ERC-721, and SPL. DeFi work covers staking, vesting, escrow, and wallet integration with ethers.js. dApps are TypeScript, React, Next.js, Node.js, Fastify, PostgreSQL, and Python. Contracts ship with tests, access control, gas review, and a verified deployment. I integrate fiat on-ramps and off-ramps for wallets, exchanges, and fintech apps - widgets, direct APIs, KYC handoff, webhooks, and reconciliation. On-ramp and off-ramp providers I work with: MoonPay, Ramp Network, Transak, Banxa, Mercuryo, Alchemy Pay, Coinbase Pay, Binance P2P, Onramper, Meld, Bridge.xyz, Rain.xyz, Circle. I implement KYC and KYB with Persona, Sumsub, Rain.xyz, and Bridge.xyz - identity checks for users and business verification for companies, including the handoff into the ramp or your own compliance flow. Master of Information Technology. 20+ years designing and building production systems.