Software Developer (Trading Engine)

We're Hiring: Senior Blockchain Engineer 🚀 Location: Porto, Portugal (Hybrid) [EU]Join Only High IQ as we revolutionize blockchain infrastructure! We're seeking a Senior Blockchain Engineer to take technical ownership of our critical transaction system. Company DescriptionOnly High IQ is a hub for innovative minds, fostering collaboration and creativity to develop groundbreaking technological solutions. Our mission is to transform visionary ideas into reality, uniting exceptional talent to shape the future. We thrive on intelligence, creativity, and innovation to pioneer advancements and revolutionary platforms. Join us to be part of a dynamic community at the forefront of technological development. The RoleAs our Senior Blockchain Engineer, you'll be the guardian of our transaction ecosystem - maintaining and evolving the infrastructure that powers high-volume blockchain operations. You'll work with embedded wallet systems and a custom onramping solution, ensuring seamless user experiences from funding to transaction completion. What You'll Do🔹 Own the complete transaction lifecycle - from creation to execution and status transitions🔹 Ensure post-transaction integrity through robust confirmation and reconciliation processes🔹 Maintain and enhance embedded wallet systems and onramping infrastructure🔹 Implement and manage transaction sponsoring mechanisms (gas sponsorship)🔹 Strengthen system safety with replay protection and reprocessing strategies🔹 Build and maintain blockchain interfaces for product backends Required Technical Expertise🔸 Deep Solidity and EVM architecture experience🔸 Expert-level proficiency with Hardhat/Foundry🔸 Strong command of Ethers.js, Viem, or Wagmi🔸 Proven track record managing on-chain/off-chain integrations🔸 TypeScript mastery for backend services🔸 Foundational AWS knowledge (Lambda, EC2, Cognito, Postgres, DynamoDB) Our Tech StackBlockchain Core: Solidity, Hardhat, Foundry, Ethers.js, Viem, WagmiBackend: Node.js, ExpressJS, TypeScript (DDD/Hexagonal patterns)Infrastructure: AWS (Cognito, Lambda, EC2, IAM), Aurora/Postgres, DynamoDB, Neptune Your MissionEnsure reliability, traceability, and production readiness for our high-volume ecosystem. You'll join at an exciting time, building on an established codebase while shaping the future of our infrastructure.Ready to build something extraordinary? Apply now or tag someone who'd be perfect for this role! 👇#BlockchainJobs #CryptoCareers #SeniorEngineer #PortoJobs #TechHiring #BlockchainDevelopment #EVM #Solidity #OnlyHighIQ

We are looking for a skilled DApp & Smart Contract Developer to enhance and stabilize our client’s crypto vesting platform. You will diagnose existing issues, improve performance, deliver new features, and ensure seamless coordination between smart contracts and the front end.
This role is ideal for someone who thrives in fast-moving environments, values clean and secure code, and understands the nuances of blockchain-based application architecture.
Responsibilities
Diagnose and resolve issues in vesting smart contracts and their front-end integrations.
Implement new features and system enhancements to improve UX and overall platform performance.
Maintain smooth interaction between the web interface and deployed smart contracts.
Conduct testing, audits, and deployments across testnet and mainnet environments.
Optimize contract logic for performance, security, and gas efficiency.
Collaborate with our engineering team to identify pain points and deliver stable, secure solutions.
Requirements
Proven experience building full-stack decentralized applications.
Strong proficiency in Solidity, JavaScript/TypeScript, and modern frameworks (Angular, React, or Vue).
Hands-on experience with Hardhat or Foundry for smart contract development and testing.
Familiarity with Ethers.js or Web3.js for blockchain interaction layers.
Solid understanding of Ethereum, Polygon, or other EVM-compatible chains.
Experience integrating wallets such as MetaMask and managing on-chain/off-chain data flows.
Strong debugging skills, attention to detail, and a security-first mindset.
Nice to Have
Experience with smart contract security audits and gas optimization techniques.
Knowledge of Node.js-based backend services or API integration layers.
Previous experience with vesting, staking, or token distribution mechanisms.
Project Scope
This role supports a short-to-mid-term initiative focused on stabilizing and enhancing an existing crypto vesting platform. High-performing developers may have opportunities for ongoing collaboration across additional blockchain and product engineering projects.
Hiring Process
Technical Assessment - Selected candidates will complete a short, clearly scoped technical exercises designed solely to evaluate coding approach and smart contract knowledge.
CTO interview - A final discussion to evaluate technical reasoning, architectural thinking, and team fit. Successful candidates may receive an offer through Contra following this conversation.

About the Job
We're looking for a Senior Blockchain Developer with strong Ethereum/PulseChain smart contract experience to work on our DeFi/GameFi platform. You'll be building and maintaining betting contracts, yield farming mechanisms, token swap systems, and Web3 frontend integrations for our decentralized application on PulseChain.
Key Responsibilities
Smart Contract Development
System Architecture & Integration
Frontend Web3 Integration
Security & Compliance
Performance & Monitoring
Required Technical Skills
Blockchain Expertise
Frontend Web3 Development
Development Tools
Integration & Tools

Senior Go Developer (Crypto focus; remote) The company (name withheld till the interview stage) is a non-custodial staking, re-staking, and node hosting platform that delivers advanced, secure infrastructure for institutional and retail investors. With automated services and an intuitive interface, we simplify the process of running full nodes, masternodes, and validators across 77 Proof-of-Stake blockchain protocols, hosting tens of thousands of nodes globally.In addition, we contribute to the blockchain ecosystem by offering complimentary tools and RPC endpoints for over 100 blockchain protocols, enabling users and developers to engage with their preferred blockchain networks and build innovative solutions!We are seeking a strong Senior Go Developer with experience in cryptocurrency. Requirements:Cryptocurrency and Node Experience: Minimum 1.5–2 years of experience working in the cryptocurrency space, specifically with nodes.Extensive experience and expertise in Go development.Russian or Ukrainian language proficiency.Knowledge of Node.js is a plus.Experience working in a remote, asynchronous environment.Familiarity with Slack for communication and collaboration.Working hours:You may start your 8-hour working day between 7 and 11 am GMT+3. For example, from 9 am to 5 pm GMT+3, etc.Remote team spanning from Los Angeles to London to Dubai, with minimal calls and Slack-based communication & decision-making.The team consists of 6-10 members with a strong sense of commitment—many have been with us for over 7 years. What we offer:Full-time job (8 working hours per day, Monday-Friday).Remote work. You may be located in any country, just need a good Internet connection, a powerful computer to work from, and the opportunity to adjust your working schedule for the team.Be part of a fast-growing, highly respected company in the crypto industry.Stability. This is not project work, we consider only the candidates looking for a long-term commitment of 1.5+ years.Work autonomously with a team of like-minded professionals.Engage in challenging and innovative projects with cutting-edge blockchain technologies.Salary will be discussed during the interview. Paid in USDT. Application deadline: ASAPSelection process:1. Fill in the application form - attach your CV & a GitHub portfolio link;2. Have a Zoom interview with Hire5 Recruiter;3. Have a technical Zoom meeting with the developer from the company team;4. Have a quick Zoom interview with the CEO of the company;5. Get hired!

📌 Job Description
 
We are building a production-ready Web3 waitlist and dashboard platform using Next.js 15 (App Router), BSC Testnet, Supabase, and Wagmi v2.
The core architecture, database schema, and feature roadmap are already defined. We are looking for an experienced developer to complete, polish, and harden the project.
 
This is not a prototype — the goal is a fully working, deployable system with clean code, security best practices, and proper Web3 UX.
 
🧩 Project Overview
 
The platform includes:
Wallet-based user registration (BSC Testnet only)
Automatic network detection & switching
Supabase-backed user management
Automatic virtual card generation (Bronze / Silver / Gold)
Token staking system with transaction logging
Referral system with rewards tracking
Dashboard with analytics & history
X (Twitter) OAuth integration
Discord bot with XP & invite tracking
A detailed README and database schema are already prepared.
 
✅ Responsibilities
 
You will be responsible for:
 
Completing and stabilizing the Next.js App Router implementation
Finalizing wallet connection & network enforcement (Chain ID 97)
Ensuring Supabase RLS policies are correct and secure
Implementing or completing:
Staking flows (stake, unstake, claim, emergency withdraw)
Referral tracking & reward logic
Dashboard analytics & transaction history
Finalizing X (Twitter) OAuth integration
Reviewing and improving overall code quality & structure
Fixing bugs, edge cases, and UX issues
Preparing the app for Railway deployment
(Bonus) Improving performance and Web3 UX
 
🛠 Tech Stack (Must-Have Experience)
 
Required:
 
Next.js 14/15 (App Router)
TypeScript
Wagmi v2 + WalletConnect
EVM chains (BSC preferred)
Supabase (Postgres, RLS, triggers, SQL functions)
Tailwind CSS
Web3 transaction handling & logging
 
Nice to Have:
 
Discord bot development (Node.js)
OAuth 2.0 (X / Twitter)
Smart contract interaction (staking contracts)
Framer Motion
shadcn/ui / Radix UI
 
🔒 Security Expectations
 
You must be comfortable with:
Wallet validation & chain enforcement
Preventing self-referrals & abuse
Transaction hash uniqueness checks
Secure handling of OAuth tokens
Supabase RLS & role-based access
 
📦 Deliverables
 
Fully working, deployable application
Clean, documented codebase
Verified Supabase schema & policies
Functional staking & referral systems
Deployment-ready build (Railway)
Basic handover documentation
 
⏳ Timeline
 
Estimated duration: 2–4 months
Start: Immediately
Potential for long-term collaboration
 
💰 Budget
 
Open to fixed-price or hourly
Please include:
 
Your estimated timeline
Relevant Web3 / Next.js projects
Any questions or suggestions to improve the system
 
🧠 How to Apply
 
When applying, please answer:
 
Have you built production Web3 apps with Next.js + Wagmi before?
Have you worked with Supabase RLS & SQL triggers?
Share 1–3 relevant projects (GitHub or live links)
What risks or improvements do you see in this architecture?
Generic proposals will be ignored.