Senior Software Engineer (Backend & API Services)

We are Nebula Nodes, building a high-performance L2 protocol. We are looking for an engineer who understands the difference between "writing a smart contract" and "designing a scalable ecosystem".
 
Protocol Core: Development and optimization of L2-settlement logic on Solidity/Yul.
 
Bridge Security: Designing secure cross-chain gateways with protection against double spending and reorgs.
 
Node Infrastructure: Optimizing the interaction of node validators with the EVM stack.
 
Gas Engineering: Extreme cost reduction for publishing data in L1 (Deneb/Cancun-ready).
 
Requirements:
Deep knowledge of Solidity (0.8.20+) and Assembly (Yul).
 
Experience working with Foundry (Fuzzing/Invariants) and understanding the architecture of OP Stack or Arbitrum Orbit.
 
Skills of working with indexers (The Graph/Envio) and the RPC layer.

Just as the job description say's, you will work as a social media manager, and help me meet daily target's without fail. You must show your willingness to work 

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