Back End Developer Engineer

At UNYX AI, we are building a secure, institutional-grade programmable settlement and routing infrastructure for NBFIs, EMIs, PSPs, custodians, and market makers. We operate a high-density, low-latency environment with maximum engineering rigor and zero corporate bureaucracy. This is a pure builder role for an engineer who wants to stay deep in complex algorithms, distributed ledger codebases, and strict financial data structures—not a people manager or a DevOps administrator. A full-time, long-term contract as an independent service provider. Remote-first flexibility with structural alignment in the UK, NL, or PT time zones.

Highly Competitive Compensation: Premium contract rates tailored for top-tier engineering talent capable of maintaining strict mathematical determinism under real-world conditions.

You will own the backend engineering domain for our core transaction orchestration and financial data architecture:

• Design and implement highly optimized pathfinding pipelines (utilizing Dijkstra on directed graphs weighted by delivered quote metrics) to calculate real-time, multi-hop conversion paths (≥3 hops) across fiat corridors and tokenized assets.
• Architect Low-Latency Bidding Logic: Program our continuous RFQ loop aggregation system, managing asynchronous quote fanouts, partial fills, deterministic maker selection scoring (weighted price, inventory, latency, reputation), and multi-hop route recomposition.
• Engineer the Distributed Double-Entry Ledger: Direct our split-storage ledger layer, pairing specialized systems like TigerBeetle (for immutable, ultra-high-performance debits, credits, and code bitmasks) with an operational PostgreSQL sidecar acting as a high-speed read model.
• Model Complex Financial Mathematical Behaviors: Build code handlers to execute precise programmatic fee strategies—translating complex multi-tenant data structures like Affine linear models, cliff tiering, progressive tranche splits, and min-max collar clamps into deterministic rounding logic.
• Enforce State-Machine Atomicity & Failure Rollbacks: Build idempotent saga execution patterns handling per-hop atomicity, dynamic timeout mitigations (quote TTL tracking), and compensation simulations that execute placeholder reversing entries if a mid-route settlement aborts.
• Manage Financial Edge Cases: Abstract network transaction anomalies (on-chain gas burning, pool slippage, and variance balances) by capturing actual confirmation webhooks before writing immutable entries.

Qualifications:

• FinTech or Quantitative Core Veteran: You have years of experience deep within financial execution engines, ledger accounting boundaries, or electronic communication networks (ECNs).
• Master of Complex Data Structures: You navigate structured polymorphic schemas easily (such as heavily nested ISO 20022 payloads or multi-layer JSONB configuration manifests) and enforce data validation discipline at the application boundaries.
• Deeply AI-Native Builder: You don't just copy-paste from LLMs; you use agentic coding loops, automated simulations, and advanced scripting daily to fuzz-test code paths, inject transactional faults, and validate data topology at scale.
• Core Languages: Strong production proficiency in fast, strongly-typed systems languages—specifically Go (Golang), Rust, C++, or robust modern JVM environments (Java/Kotlin).
• Expert-level PostgreSQL (complex JSONB modeling, recursive queries, row-level concurrency locking) and experience with or strong interest in TigerBeetle or similar specialized financial databases.