Senior+ Backend Engineer

bringing imagination to life for kids nationwide! The technical challenge is real. We’re running real-time streaming, processing thousands of concurrent connections from IoT devices, and orchestrating ML pipelines that return magical responses in seconds or less. Our hybrid Python-Elixir architecture handles everything from device authentication to job queuing to image delivery, all with the reliability parents expect and the speed kids demand. We need a Backend Engineer to own and evolve this infrastructure. You’ll architect and maintain the systems that connect thousands of devices, manage real-time audio pipelines, and power the experiences that make everything just work. This is a foundational role where your decisions will shape how we grow from thousands to millions of users. Real-Time Infrastructure

IoT w/ audio streaming that handles tens of thousands (on our way to millions) of concurrent device connections Distributed job systems with Redis queues and pub/sub Optimized pipelines for GenAI at high RPM with sub-second latency Monitoring and observability to keep our infrastructure healthy

APIs & Services

FastAPI services for device auth, user management, and webhook integrations Secure RESTful APIs that are a joy to work with Reliable integrations with external ML services Data pipelines that feed our evaluation systems

5+ years building and shipping backend systems in Python Deep experience with FastAPI and asyncio patterns Strong PostgreSQL skills, including schema design Hands-on experience with Redis (caching, queues, pub/sub) Track record of designing reliable distributed systems A DevOps mindset, comfortable deploying, monitoring, and scaling Experience with GenAI/LLM pipelines deployed in production Clear communication skills; can translate technical tradeoffs for the team

Backend Engineer Own, evolve, and scale the real-time infrastructure behind Stickerbox: an AI-powered voice-to-sticker printer already serving thousands. About Hapiko Hapiko is a Brooklyn-based company building the future of play. Description Founded by Arun Gupta (former CEO of Grailed, which sold to GOAT Group in 2022) and Bob Whitney (Anthropic, NYT Games), we’re on a mission to create safe, hands-on AI experiences that fuel kids’ imaginations rather than replace them. Our first product, Stickerbox, is the world’s first voice-to-sticker printer. A device that instantly transforms a child’s spoken ideas into printable, colorable stickers. We sold out our first run shipping for the holidays, and additional batches beyond that. It’s already being called “one of the first products to make AI feel magical for kids and grounded for parents.” We have a $7M funding round led by Maveron (backers of Lovevery), Serena Ventures, and Ai2 (The Allen Institute). Stickerbox is already in homes, Worked with Elixir/Phoenix and enjoy managing concurrency Built software for IoT or custom hardware devices Managed real-time systems and streaming data Experience with streaming protocols and media formats Tuned ML pipelines with prompt engineering and evals

Our stack

Backend: Python, FastAPI, Elixir/Phoenix Data: PostgreSQL, Redis Infra: Docker

Location: NYC only, On-site (flexible on WFH but we like to be in office the majority of the week) in our Brooklyn based office, close to most major train lines. Salary: $150,000 - $250,000 per year