The Role
As a Senior Engineer, you'll develop scalable, event-driven backend architectures, design low-latency APIs, and contribute to product development across the stack while optimizing performance and collaborating on AI features.
Summary Generated by Built In
🚀 About Supersonik
Supersonik helps B2B SaaS companies sell faster with AI-powered product demos. On a live video call, our AI Agent shares the screen to walk buyers through a personalized, interactive demo in any language. This lets teams skip long sales calls and focus on closing deals.
We’re backed by Andreessen Horowitz (a16z) and work with leading SaaS companies worldwide.
🧩 About the Role
We’re hiring Senior Engineers to join our core team in Barcelona.
You’ll be solving complex, technical problems and shaping the product and architecture from day one. You should thrive in high-growth startup environments, be fluent in modern Python and async programming and know how to build scalable, event-driven systems. You care about fast, real-time systems and enjoy working at the intersection of performance, AI and great user experience.
If you love solving first-principles problems, navigating ambiguity and want to build a product people love you’ll fit right in.
- Scale a real-time, event-driven backend architecture where milliseconds matter
- Design and implement low-latency APIs using FastAPI and Asyncio
- Solve engineering challenges in performance optimization, observability, and resilience
- End to end contributions from frontend to infrastructure.
- Collaborate on prompt engineering, LLM behaviors, LLM fine-tuning and UX
- Build and maintain infrastructure-as-code with Terraform and AWS
- Contribute to 0→1 product development with a small, fast-moving team
- Backend: Python, FastAPI, Asyncio, Redis, PostgreSQL
- Infra: AWS, Terraform, CI/CD
- Frontend: React
- Tooling: GitHub, Datadog, Linear
- Experience with LLMs (prompting, training, alignment)
- Experience with TTS, STT and real-time voice
- Experience with browser automations
- Deep knowledge of AWS, Terraform, and distributed systems
- Experience shipping 0→1 products in a startup
- Significant equity in a company backed by A16z
- Full ownership, real impact, and fast learning cycles
- A tight-knit team that values clarity, speed, and smart execution
Top Skills
Asyncio
AWS
Ci/Cd
Datadog
Fastapi
Git
Linear
Postgres
Python
React
Redis
Terraform
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The Company
What We Do
Supersonik is reshaping how B2B SaaS companies sell their software. Our AI Agents deliver instant, personalized, interactive, and multi-language product demos at scale, combining the discovery, qualification, and demonstration steps for a faster sales cycle and increased revenue. We’re replacing outdated sales cycles with smart, dynamic AI-driven experiences, and we’re just getting started.
