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Y Combinator

Senior Full Stack Engineer

Salary$180k – $250k
LocationSan Francisco, California, US
Work modeon-site
Typefull-time
Company size201–500 people
First seen1w ago
Last seen2d ago
Mission:
Sphere has built the world’s first AI-native tax engine that helps companies like Eleven Labs, Replit, Runway AI, Windsurf (+ many more) automate their sales tax, VAT and GST obligations:
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We’re growing rapidly (34%+ MoM revenue growth) and helping the fastest growing tech companies around the world including Eleven Labs, Replit, Windsurf, Fathom, Linktree, Photoroom, Sierra AI, Zed etc
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We’ve spent the last 1.5 years building local rails into tax authorities in both the US and internationally to properly automate compliance processes (no other vendor has done this)
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We’re building the world’s first AI-native tax engine (which will be the foundation for a broader cross border compliance platform; think Deel for international billing)
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We’re well funded by Felicis Ventures and YC
About the role
Sphere is looking for a versatile full stack engineer who can jump on different mission critical areas to help accelerate its production - e.g. filing infrastructure, tax engine and new product areas (input tax, withholding tax, e-invoicing).
These areas are key levers towards scaling Sphere and growing ARR, meaning that your work will have a direct impact on the growth of the business
Why this is a massive opportunity:
🌍 Massive TAM: Every business around the world needs this. Compliance isn’t optional.
🌬️ Strong macro tailwinds: Businesses are expanding globally at a faster pace, while tax authorities are cracking down on cross-border compliance, driving urgent demand.
✨ AI advantage: Incumbents can’t scale beyond the U.S.; our AI-native tax engine can.
🔮 Product vision: Indirect tax is just the start; we’re building the Deel for international billing.
What you will do:
Within weeks:
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Ship features related to a key component of Sphere’s platform - e.g. filing infrastructure
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Own and manage this key component, driving measurable outcomes
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Work directly with customers like Eleven Labs, Replit and Windsurf to improve / optimize that key component of the platform (e.g. improve filing generation and submission speed [x]%)
Within months:
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Develop expertise across other key components of Sphere’s platform - e.g. tax engine, new products - to manage and execute improvements in this area
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Lead / mentor additional engineers in component areas that you have worked in
What’s important to us:
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The Dog: Grit > pedigree.
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Ship fast: If it can be done today, do it today.
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Self-starter: No hand-holding
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Accountability: You’ll be held accountable to objective, measurable targets each month.
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In-person: SF only.
Requirements:
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Strong experience in Python . Our core application backend and data pipeline services are built with Python and Django
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While frontend / React may not be your primary focus, you’re not afraid to dive in when needed
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Very strong attention to detail. When you work with numbers this is a non-negotiable - it’s not enough to be 99% right.
Nice to have
Nice to have:
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Experience working with large volumes of transaction data. You’ll be getting very familiar with it!
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Experience with Django or Python ORM
More roles at Y Combinator
Forward Deployed EngineerStaff Software EngineerFull Stack Product Engineer - Remote/USSenior/Staff Backend EngineerWireless Network Engineer
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