Senior Back-End Developer

About The Company Hercle is a fast-growing fintech building institutional-grade infrastructure that bridges fiat, stablecoins, and digital assets, enabling cross-border payments and banking infrastructure for global trade.

About The Company Hercle is a fast-growing fintech building institutional-grade infrastructure that bridges fiat, stablecoins, and digital assets, enabling cross-border payments and banking infrastructure for global trade. Serving over 200 clients globally, Hercle provides banks, brokers, payment service providers, fintechs, commodity traders, corporate treasuries, and other NBFIs with seamless solutions for cross-border payments and treasury management.

Working at Hercle

We're a lean, flat team where ideas matter more than titles and everyone gets real responsibility from day one. You'll solve complex problems at the intersection of global finance and digital assets, for some of the world's largest institutions and corporates. If you're curious, driven and excited to shape how money moves globally, we'd love to meet you.

About The Role

We're looking for a Senior Back-End Developer to join our Trading squad, which owns Hercle's trading and FX product. Our ambition: the most competitive institutional FX and digital-asset trading offering on the corridors that matter to our clients, on quote quality, client experience and operational efficiency.

Key Responsibilities

• Design, build and operate low-latency services for order management, RFQ and execution across multiple liquidity venues and providers
• Build and evolve our tokenised products offering (e.g. DeFi vaults, tokenised MMFs), from subscription and redemption to on-chain settlement and position tracking
• Scale our Price API and market data pipelines for accurate, fast and resilient institutional quotes
• Automate the trade lifecycle end to end, from order capture to fees, booking and settlement, across traditional and on-chain rails
• Turn trading-desk workflows into robust, auditable software, with product and compliance
• Write clean, documented code, review peers' work, fix bottlenecks and bugs, and improve CI/CD

How We Build

Every squad works on our two C# code bases: the Execution API, the client-facing gateway exposing documented REST and real-time WebSocket (SignalR) APIs, and the Back Office API, used daily by Operations, Compliance and the trading desk. Behind them sits a fleet of domain microservices and provider integrations.

• .NET 10 microservices over gRPC; event-driven internals with CQRS, domain events and background jobs
• AWS throughout: EKS, DynamoDB (in-memory caches on the hot path), Cognito, OpenSearch, S3
• Azure DevOps CI/CD, with integration tests run against real deployed environments
• AI-first engineering: agents write and refactor code, review every PR and help investigate incidents

What You Will Work On

You own the latency-critical part of the platform: everything a client touches between asking for a price and seeing a trade booked.

• Client-facing trading APIs: WebSocket streaming and execution, REST endpoints, real-time web app views
• Orders, RFQ and two-way quote execution, where every millisecond and allocation counts
• Price API, market data and the services behind them: orders, trades, quotes, fees, settlement
• Desk tools (exposure limits, fees, pair rules) and integrations with venues, execution platforms and backtesting

Requirements

• Bachelor's degree in Computer Science, Engineering or a related technical field
• 5+ years building back-end systems in a strongly typed language (e.g. C#/.NET, Java, Kotlin, Go), ideally in trading, fintech or digital-asset environments
• Strong grasp of OOP, design patterns, distributed systems, concurrency, multithreading and performance optimisation
• Experience with SQL and NoSQL databases, CI/CD, Git and testing frameworks
• Strong problem-solving, attention to detail and ownership in a fast-paced environment
• Daily, hands-on use of AI coding agents on production work (not just autocomplete), with the judgement to give them the right context and to review and own what they produce
• Fluent written and spoken English

Nice to have

• Strong C#/.NET experience , ideally including low-allocation, high-performance code (Span, pooling, hand-built serialisation)
• Familiarity with electronic trading, FX, market making or brokerage systems (OMS/EMS, RFQ, smart order routing, FIX), with knowledge of pricing, spreads, order books and pre/post-trade controls
• Experience with real-time services with many concurrent WebSocket connections, and market or time-series data at scale
• Knowledge of tokenised products and DeFi vaults, including on-chain integratio