Full-Stack Web3 Engineer (USDC)

The Role
We are looking for a Full Stack Engineer to take full ownership of building a non-custodial crypto payment gateway for USDC on Ethereum. You will not just be "writing code" from a ticket; you will be responsible for the entire delivery, including infrastructure, security, database design, and the admin dashboard.
You are effectively acting as the Founding Engineer/CTO for this build. You must be comfortable making architectural decisions, setting up CI/CD, and securing a financial application.
The System
A compliant, on-chain payment rail that:
Generates unique, one-time deposit addresses for users (HD Wallets).
Detects incoming USDC transactions (Chain Indexing).
Sweeps funds to a central treasury using EIP-3009 (Gasless Permits) to minimize ETH usage.
Provides a secure Admin Dashboard for monitoring and reconciliation.
Scope of Work (End-to-End)
1. Architecture & Infrastructure (DevOps)
Cloud Setup: Set up the production environment (AWS/GCP/DigitalOcean) using Docker/Kubernetes or robust container orchestration.
Security: Configure AWS KMS / HashiCorp Vault for secure key signing (no private keys in DB). Configure firewalls and rate limiting.
CI/CD: Setup automated testing and deployment pipelines (GitHub Actions).
2. Backend Development (Node.js/TypeScript)
API: Build the REST API (NestJS/Fastify) for merchant payment intents and webhooks.
Workers: Build the fault-tolerant "Watcher" (indexing) and "Sweeper" (fund movement) services.
Database: Design and migrate the PostgreSQL schema for high-integrity financial records (idempotency, audit logs).
3. Frontend Development (React/Next.js)
Admin Console: Build a secure, internal dashboard to view payment flows, manual sweep overrides, and system health (e.g., "Low Gas" alerts).
4. QA & Handoff
Testing: Write an E2E test suite using Hardhat/Anvil (forking Mainnet) to simulate reorgs and edge cases.
Documentation: Deliver API docs (Swagger/OpenAPI) and a "Runbook" for operations.
Tech Stack Requirements
Backend: TypeScript, Node.js (NestJS preferred), PostgreSQL, Redis.
Web3: Ethers.js v6 / Viem, Hardhat (for testing).
Frontend: React / Next.js / TailwindCSS (for Admin UI).
Infra: Docker, AWS (EC2/ECS, RDS, KMS), Terraform (optional but preferred).
Who You Are
A "Finisher": You don't just write functions; you ship products. You handle the messy parts (migrations, deployment scripts, error handling).
Security-First: You understand why "storing a private key in an environment variable" is an instant disqualification.
Senior Experience: You have deployed Ethereum-based applications to mainnet before and understand gas management, reorgs, and RPC reliability.

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