Senior Backend Engineer (Infrastructure) at Sphere

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: 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 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) 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) We're well funded by Felicis Ventures and YC As Sphere scales to support millions of customer transactions globally, the need for scalable infrastructure to support transaction syncing and live tax calculation within checkout and invoices is paramount. Given we are a key part of mission critical billing flows for some of the fastest growing companies in the world, availability, resilience and speed are all key areas of focus that this role would