Software Engineer, Singapore

Job Title: Software Engineer Department: Engineering & Product Development (EPD) Reports to: Engineering Lead Location: Singapore (Hybrid work arrangement) About Codex Codex is building the infrastructure for stablecoin-based cross-border payments — moving money faster, cheaper, and more transparently than the legacy financial system. Backed by Circle, Coinbase, Dragonfly, Wintermute, and Cumberland, we're a small team solving hard problems at the intersection of crypto and global payments. The Role You'll own the full lifecycle of how money moves through Codex — from the moment a customer onboards, through KYC/KYB and compliance checks, all the way to payment execution and settlement. You'll work directly with the founders and with our Trading Ops and Compliance teams to build systems that are fast, reliable, and compliant across every market we operate in. You'll have real influence over architecture, real ownership of a critical domain, and you'll be building things that matter from day one. Responsibilities 3P & Payment Integrations - Own the technical integration of third-party payment providers, including offramp/payout flows, API integration, and sandbox/testnet testing - Design and implement the architecture for how 1P and 3P flows interact, with careful consideration of coupling, maintainability, and risk - Integrate payment rails across the globe — banks, PSPs, and liquidity providers - Build the document storage and invoice pipeline to support 3P operational workflows - Coordinate with Legal and Compliance on open questions arising from 3P integration (e.g. balance holding, regulatory implications) Settlement, Reconciliation & Stablecoin - Build and maintain settlement, reconciliation, and ledger systems across fiat and crypto flows - Build stablecoin on/off-ramp flows and the crypto-specific compliance tooling that supports them Backend Architecture - Lead significant backend refactors to improve system correctness and maintainability - Design and mainta