Fullstack Engineer - Known

Praxis, Inc.; San Francisco (CA); On-site; USD 180,000 - 280,000; Full time

Job summary

Praxis, Inc. is seeking a technical co-founder to own the full stack for Known, a consumer AI dating product built from the ground up with a focus on delightful UI, robust data flows, and seamless integrations.

You will partner with AI/ML, product, and design teams to translate ambitious ideas into production code, shaping millions of user experiences and leading critical architectural decisions.

Qualifications

• 3-5 years building production fullstack or mobile applications, ideally in consumer products or startups.
• Strong proficiency in TypeScript, React, React Native, and Node.js
• Experience designing and scaling RESTful APIs with attention to performance, security, and maintainability.
• Strong working knowledge of Postgres - you're comfortable with data modeling, queries, indexes, and database performance.
• Experience with cloud platforms (AWS, GCP, Vercel, Railway) for deployment and infrastructure.
• Comfortable with modern development workflows: Git, CI/CD, feature flags, monitoring, and incident response.
• Familiarity with WebSockets and WebRTC for real-time communication is a plus.
• Passion for user experience and product quality - you'll care about polish, speed, and edge cases.

Responsibilities

• Build and ship mobile experiences in React Native that are fast, delightful, and accessible - from onboarding flows to real-time messaging and match discovery.
• Design and maintain backend services in Node.js/TypeScript, including RESTful APIs, WebSocket connections for real-time chat, and WebRTC integrations for audio/video experiences.
• Integrate third-party platforms (OpenAI/Anthropic LLMs, Apple/Google Pay, reservation systems, SMS/push notifications) to deliver seamless, automated experiences.
• Collaborate with AI/ML engineers to surface model outputs - compatibility scores, personalized recommendations, conversational agents - through intuitive UI and performant APIs.
• Own infrastructure and deployment using modern cloud platforms, ensuring reliability, security, and scalability as we grow.
• Implement analytics and instrumentation to measure user engagement, conversion funnels, and product health in real time.

Skills

TypeScript

React

React Native

Node.js

RESTful APIs

WebSockets

WebRTC

Cloud platforms

CI/CD

Git

Tools

OpenAI

Anthropic LLMs

Apple Pay

Google Pay

AWS

GCP

Vercel

Railway

Job description

About the Role

You'll be a core technical founder building the entire product surface of Known - from the mobile app users fall in love with, to the backend systems that power matching and conversation, to the API integrations that make dating effortless. You'll ship features that blend beautiful UI, intelligent data flows, and third-party services into a cohesive, consumer-grade experience that feels magical.

You'll work closely with the founding team (AI/ML, product, and design) to translate ambitious product ideas into production code. This is a high-ownership role where you'll architect systems, make critical technical decisions, and directly shape how millions of users experience Known.

Responsibilities

• Build and ship mobile experiences in React Native that are fast, delightful, and accessible - from onboarding flows to real-time messaging and match discovery.




• Design and maintain backend services in Node.js/TypeScript, including RESTful APIs, WebSocket connections for real-time chat, and WebRTC integrations for audio/video experiences.




• Integrate third-party platforms (OpenAI/Anthropic LLMs, Apple/Google Pay, reservation systems, SMS/push notifications) to deliver seamless, automated experiences.




• Collaborate with AI/ML engineers to surface model outputs - compatibility scores, personalized recommendations, conversational agents - through intuitive UI and performant APIs.




• Own infrastructure and deployment using modern cloud platforms, ensuring reliability, security, and scalability as we grow.




• Implement analytics and instrumentation to measure user engagement, conversion funnels, and product health in real time.

Requirements

• 3-5 years building production fullstack or mobile applications, ideally in consumer products or startups.




• Strong proficiency in TypeScript, React, React Native, and Node.js.




• Experience designing and scaling RESTful APIs with attention to performance, security, and maintainability.




• Strong working knowledge of Postgres - you're comfortable with data modeling, queries, indexes, and database performance.




• Experience with cloud platforms (AWS, GCP, Vercel, Railway) for deployment and infrastructure.




• Comfortable with modern development workflows: Git, CI/CD, feature flags, monitoring, and incident response.




• Familiarity with WebSockets and WebRTC for real-time communication is a plus.




• Passion for user experience and product quality - you'll care about polish, speed, and edge cases.

Example Projects

• Design a reservation and payment integration layer that allows users to book dates, split costs, and receive confirmations - all within the app.




• Create a real-time messaging system with typing indicators, read receipts, and optional AI-powered conversation starters using WebSockets and streaming LLM responses.




• Build WebRTC infrastructure for voice and video chat between users and AI voice agents during onboarding and matching conversations.




• Develop a modular component library for personalized UI cards (match suggestions, date ideas, conversation prompts) powered by ML model outputs.




• Implement a feature flagging and A/B testing framework to enable rapid experimentation across mobile and web surfaces.




• Expand the admin dashboard with new functionality for monitoring user activity, system health, and ML model performance metrics.

Why This Role

This is a chance to be a technical co-architect of a consumer AI product from the ground up - to own the entire stack and ship features that directly impact how people meet, connect, and fall in love. You'll work at the intersection of design, data, and AI, with the autonomy to build systems your way and the responsibility to make them world-class.