Senior Backend Engineer

Senior Backend Engineer - Billing About Hydra Host Hydra Host is a Founders Fund-backed NVIDIA Cloud Partner building the infrastructure platform that powers AI at scale. We connect AI Factories — high-performance GPU data centers — with the teams that depend on them: research labs training foundation models, enterprises running production inference, and developer platforms demanding scalable compute capacity. At our core, Hydra is a financial and settlement layer for AI physical infrastructure. We process and reconcile hundreds of millions of dollars across complex contracts, usage-based consumption, and real-world operational constraints. Correctness, transparency, and trust are not nice-to-haves — they are the product. The Role We are hiring a Senior Billing Engineer to own and build the financial backbone of the Hydra platform. This is not a SaaS billing role. This is not “just integrate Stripe.” We sit at the intersection of physical GPU infrastructure, multi-party contracts, and real money movement. Every GPU server, every second, every credit, every payout must be traceable, auditable, and correct. Your mandate is to make billing a competitive advantage for Hydra: fast and accurate payouts to data center partners, absolute confidence in invoices for renters, and a system that can scale with the complexity of the AI infrastructure market. You will design and implement systems that account for every dollar, handle failure modes gracefully, and turn messy real-world contracts into accurate & reliable financial flows. What You’ll Do Act as a hands-on senior backend engineer owning production billing systems end to end Own the design and implementation of Hydra’s end-to-end billing engine and settlement systems, writing and operating production backend services Build and maintain a double-entry ledger that provides a complete, immutable paper trail for all financial activity, designed for high concurrency and strict correctness guarantees Implement contract-aware billing logic derived from infrastructure lifecycle events (provisioning, decommissioning, maintenance, etc.), including: Pre-pay and post-pay contracts Metered usage billing tied to physical GPU infrastructure Proration, refunds, downtime credits, and contract term transitions Credit limits, wallets, and burndown schedules Generate accurate invoices and earnings reports for renters and data center partners Build automated payout systems to suppliers and partners, ensuring fast and correct settlement Integrate and orchestrate money movement across payment rails (ACH, wires, RTP/FedNow, credit cards, crypto), handling retries, partial failures, and reconciliation Design for idempotency, guaranteed delivery, and reconciliation across distributed systems, including explicit handling of race conditions and double-spend prevention Partner closely with Product, Accounting, Engineering, and Operations to translate real-world contracts into robust software Anticipate and handle failure cases: partial payments, retries, reversals, delayed events, and reconciliation gaps Technical Environment Modern backend services written in TypeScript (Node.js) Event-driven and asynchronous architectures Relational databases (PostgreSQL or similar) with ACID guarantees High-precision numeric handling for financial calculations Required Qualifications Deep experience building billing, ledger, or financial transaction systems as a hands-on backend engineer Strong understanding of double-entry accounting and financial primitives (debits, credits, assets, liabilities) Experience with invoicing systems, payment processors, and money movement flows Proven ability to design resilient systems with idempotency, guarantees, auditability, and strong automated test coverage Deep experience handling concurrency, race conditions, and double-spend prevention in high-stakes financial systems Experience with event-driven or asynchronous architectures Comfort working across multiple systems and domains (product, finance, operations) High standards for data integrity, quality, automated testing Proven track record of owning complex, high-stakes systems end to end Preferred Qualifications Experience with treasury or ledger platforms (e.g. Formance, Modern Treasury, or similar) Experience automating bank integrations and payouts Familiarity with usage-based or metered billing models Experience supporting two-sided marketplaces or market exchange layers Exposure to ERP or accounting system integrations Experience working with large-scale data warehouses and financial reporting What We Value Customer obsession — accuracy and trust matter more than speed alone Principled thinking — clear mental models, explicit tradeoffs, and long-term correctness Systems thinking — you design for the whole lifecycle, not just the happy path Ownership — you see problems, drive solutions, and follow them through without being asked Technical curiosity — you want to understand how money, systems, and infrastructure really work and dive head-first to become the best Why Join Hydra Host Build the financial infrastructure that underpins the AI economy Own mission-critical systems with real-world impact and real money at stake Work alongside a senior team solving problems most companies never encounter Competitive compensation, meaningful equity, and full benefits Remote-first team with hubs in Phoenix, Boulder, and Miami, plus regular offsites The AI infrastructure layer is being built right now. If you want to own the financial systems that make it trustworthy, transparent, and scalable — this role is for you.