Software Engineer at Supersonik (Barcelona, Spain)
Supersonik· Barcelona, Spain·
Role details
Job description
🚀 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.
What You’ll Work On
- 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
Our Stack
- Backend: Python, FastAPI, Asyncio, Redis, PostgreSQL
- Infra: AWS, Terraform, CI/CD
- Frontend: React
- Tooling: GitHub, Datadog, Linear Bonus Points
- 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
What You’ll Get
- 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
Why work at Supersonik
- Culture: Described as "fast-paced, agentic AI startup" where early‑career employees get "real ownership, steep growth." The team is distributed across 5 countries (Spain, US, UK, Ireland, Germany), with an office hub in Barcelona and a smaller presence in San Francisco. linkedin.com
- Remote/Hybrid: Not explicitly stated, but the distributed workforce and two offices suggest a hybrid or remote‑friendly culture, especially for engineering and GTM roles.
- Engineering Culture: ~33% of staff are in technical roles (9 out of 25). The technical stack involves AI, real‑time systems, and security compliance, offering engineers exposure to cutting‑edge agentic AI.
- Notable Perks: Being backed by a16z provides strong runway and network. Employees get to work on a product that is already being used by a major enterprise (Salesforce). The company is still small (25 people) – offering strong ownership and impact.
- Hiring Activity: 5 open positions as of Sept 2026, including sales, operations, and AI delivery roles. linkedin.com