Codex
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 maintain order management systems: cancellation logic, state validation, and payout flows for orders with pending manual payouts
Build internal ops tooling to surface pending manual payout queues to non-engineering teams, reducing trader workload
Onboarding & Compliance Infrastructure
Build and maintain end-to-end onboarding infrastructure — KYC/KYB flows, identity verification integrations, and risk scoring
Own the KYT integration layer across fiat and crypto deposit and order workflows, in coordination with the Compliance team
Build transaction monitoring, AML, and sanctions screening systems
Maintain compliance data infrastructure — audit logs, reporting pipelines, and regulatory submissions
Implement KYT layering across 3P flows and contribute to design decisions on when and how it applies
What we're looking for
3 to 5 years of backend engineering experience, with meaningful depth in at least one of: payments/rails or compliance/onboarding
Strong system design instincts; you've built systems that handle failure gracefully and scale without becoming a maintenance burden
Experience working cross-functionally with compliance, legal, or operations teams
Comfortable with ambiguity — you can take a regulatory requirement or a business need and turn it into a well-designed technical spec
Someone who takes full ownership and moves fast without cutting corners
Nice to have
Familiarity with both payment rails and compliance frameworks
Experience in crypto or stablecoin infrastructure — on-chain settlement, blockchain analytics tooling
Prior startup or scale-up experience where broad scope was the norm, not the exception