Senior Back-End Developer (Payments)

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 Payments squad, which owns Hercle's money journeys end to end. The goal: one unified way to move money from A to B (deposits, withdrawals, transfers, transfer-outs and rebalancing), whoever is sending and whoever holds the funds. Key Responsibilities - Design and build a scalable, event-driven payment orchestration engine for deposits, withdrawals, transfers and rebalancing - Implement state machines, idempotency, retries and compensation so every money movement is safe, traceable and recoverable - Integrate orchestration with account data, provider adapters (banks, custodians, exchanges) and the core ledger - Build and operate the job fleet that automates rebalancing and recurring flows, with strong monitoring and alerting - Work with product, Operations and banking infrastructure clients to remove manual steps and improve journey success rate and speed - 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 every money movement on the platform, from the client request to the provider confirmation and the ledger entry. - Deposit, withdrawal and transfer flows over WebSocket and REST, incl. payees and crypto addresses - Banking orchestration: one canonical model routing to banks, crypto custodians and Lightning - The balance pipeline: reservations, a ledger entry per change, compensation on provider failure - Async provider states (webhooks, retries, idempotency): no payment lost or executed twice - Operations flows: approvals, rebalancing across exchanges and accounts, scheduled jobs 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) - 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 - Familiarity with payment rails (SEPA, SWIFT, Faster Payments, on-chain and Lightning) and blockchain transactions, wallets and stablecoin transfers - Experience with orchestration patterns: sagas, outbox, compensation across several external providers, message brokers (e.g. Kafka, RabbitMQ) - Knowledge of double-entry ledgers and payment reconciliation, and hands-on experience with custody APIs - Experience with AWS (EKS, DynamoDB, Cognito, IAM) and Kubernetes in production - Autonomy and ownership: you take loose problems to production in small, reviewable PRs, follow your code after release, write clearly, and work directly with Operations, Compliance and Finance - Curiosity for finance, digital assets and the regulatory side of what we build - Italian is a plus Why join Hercle? - Competitive base salary of EUR 70,000 – 90,000, depending on experience - Real ownership: in a squad with a clear problem space, you own what you ship from first idea to production - Career growth and flexible remote/hybrid working in a collaborative, forward-thinking team Interested? Reach out and send us you CV! By submitting this application, I confirm that all the information given by me in this application for employment and any additional documents attached hereto are true to the best of my knowledge and that I have not wilfully suppressed any material fact. I confirm I have disclosed if applicable any previous employment with Hercle. I accept that if any of the information given by me in this application is in any way false or incorrect, my application may be rejected, any offer of employment may be withdrawn or my employment with Hercle may be terminated summarily or I may be dismissed. By submitting this application, I agree that my personal data will be processed in accordance with Hercle's Candidate Privacy Notice