Senior Blockchain Engineer

**Location:**
Porto, Portugal (Hybrid)

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 Description**

Only 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 Role**

As 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 Stack**

- Blockchain Core: Solidity, Hardhat, Foundry, Ethers.js, Viem, Wagmi
- Backend: Node.js, ExpressJS, TypeScript (DDD/Hexagonal patterns)
- Infrastructure: AWS (Cognito, Lambda, EC2, IAM), Aurora/Postgres, DynamoDB, Neptune

**Your Mission**

Ensure 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! 👇

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