Senior Software Engineer — Core Systems & AI Infrastructure

Role Overview

Sphere is building the world’s first AI-native cross-border compliance engine, a platform that codifies and automates global tax law so companies can sell anywhere in the world and stay compliant without lifting a finger. This role is an extraordinary opportunity to join an a16z, YC, and Felicis-backed startup scaling rapidly (30%+ MoM growth) and trusted by global technology companies like Eleven Labs, Replit, Windsurf, Deel, and Lovable. You’ll build infrastructure and AI systems that solve the most complex problems in global compliance, from ingesting tax law in every market to automating registration, filing, and remittance at scale. This is regulated, high-stakes, globally distributed systems work where correctness matters and scale is non-negotiable. https://www.getsphere.com/

What You'll Do

You’ll work across mission-critical areas of the platform, including filing infrastructure, the tax engine, and new product areas like input tax, withholding tax, and e-invoicing. These systems are direct levers for ARR growth. Your work will have a clear, measurable impact on the business. You’ll own real systems, ship quickly, and be trusted to make high-stakes decisions. **Within weeks** - Ship production features on a core component of Sphere’s platform (e.g. filing infrastructure). - Take full ownership of that component, performance, correctness, reliability. - Work directly with customers like Eleven Labs, Replit, and Windsurf to improve real outcomes (e.g. reduce filing generation or submission time by X%). - Push approved tax determinations into a deterministic engine that runs in real-time with zero hallucination risk. **Within months** - Build deep context across other parts of the system: the tax engine, TRAM, and new product surfaces. - Drive improvements across scalability, accuracy, and speed in those areas. - Mentor other engineers on components you’ve owned. - Help shape how AI and deterministic systems safely coexist in regulated infrastructure.

A Typical Day Looks Like

Reviewing TRAM outputs alongside tax researchers and pushing approved logic into production. Shipping Python/Django changes that touch millions of transactions. Debugging edge-case failures across jurisdictions, currencies, and tax regimes. Jumping into React when needed to unblock a critical customer flow. Talking directly to customers about what’s broken, slow, or confusing, then fixing it.

What Success Looks Like

You own and improve a core system with measurable impact. Key metrics move because of your work (speed, accuracy, reliability). Customers notice improvements without being asked. You ship fast, and correctly. You raise the bar for engineering quality around you. You will be held accountable to objective, measurable targets every month. Be Mission Aligned: To build a generational company, we need people who think and behave differently. Pursue pain: Anything worth building requires effort and persistence. Be the dog: Relentless. Autonomous. No excuses. Ship fast: If it can be done today, do it today. Sweat the details: When working with tax and money, being 99% right isn’t enough. Bigger is better: We’re building for a global market.

Skills We Value

- Very strong attention to detail. When you work with numbers this is a non-negotiable - it’s not enough to be 99% right. Required - Strong experience with Python - Experience working on backend systems and data pipelines - High attention to detail, especially when working with numbers - Comfortable taking ownership without hand-holding - Interest in working on systems where correctness matters - Mission Aligned Nice to have - Experience with large volumes of transactional data - Django or Python ORM experience - Willingness to work across the stack when needed

The Team You'll Join

Engineers who care deeply about correctness and speed. Tax researchers who act as human guardrails for AI. Founders who sell, ship, and sit next to you in the office. A team that works in person, solves hard problems together, and celebrates wins loudly. **Life at Sphere includes:** - Annual international offsites - Live demos at Stripe Tour - Go-karts with the team - Compulsory drinks at House of Shields - Celebratory outing after closing big deals

Compensation & Benefits

Interview Process

- 30-min recruiter screen - Direct Founder Call with Nick - Technical chat - System design task + live coding - Usually onsite in the US - Can be done remotely for Australia