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Pax Historia is building a platform for worldbuilders, storytellers, and game developers to create and publish interactive 'what if' scenarios. The platform hosts 25k+ user-published presets (primarily historical simulations like 'what if Rome never fell?', with growing fantasy and sci-fi categories), has seen 92+ million rounds played, and recently raised a 10M+ seed round backed by Y Combinator (W26), Bessemer, Pace Capital, and Z Fellows.
You will be the founding engineer owning the LLM infrastructure and platform layer. This is a critical technical role: every game on Pax Historia depends on reliably sending massive numbers of requests across multiple AI providers and receiving correct responses quickly, cheaply, and reliably.
Key responsibilities include:
- Owning provider reliability, structured outputs, caching, routing, and monitoring systems
- Ensuring 37+ models reliably handle approximately 240 billion weekly tokens
- Reducing costs and latency for 60k+ daily active users
- Building systems that scale with platform growth
You will not be responsible for model training or running inference yourself; the focus is on the orchestration, reliability, and optimization layer that sits between the platform and external AI providers.
As the 7th team member, you'll have significant ownership and impact. The role requires someone obsessed with detail, data-driven, and with a strong tendency to verify everything. While you don't need prior experience with this exact system, you must be a fast learner with extremely strong fundamentals in systems design, distributed systems, or infrastructure engineering.
The team works in-person in San Francisco, 5+ days per week. Visa sponsorship is available. Compensation includes meaningful equity reflecting your responsibility as a founding engineer.
Requirements:
- Strong fundamentals in systems design, infrastructure, or distributed systems
- Detail-oriented and data-driven mindset with verification discipline
- Fast learner capable of owning complex, mission-critical systems
- Experience with API orchestration, caching, routing, or similar infrastructure preferred
- Ability to work in-person in San Francisco
