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I’m John Langas, a Senior Fullstack Engineer with 10 years of experience building scalable SaaS platforms and AI-driven features. I specialize in Next.js, Node.js, TypeScript, and cloud-native deployments, with a strong focus on multi-tenant architectures and production reliability. I have designed end-to-end systems including REST APIs, authentication layers, and Stripe-based subscription billing, and I’ve integrated OpenAI and Anthropic APIs to deliver production-grade AI capabilities in customer-facing products. I thrive on building robust, scalable architectures and collaborating with cross-functional teams to ship high-impact features.…I’m John Langas, a Senior Fullstack Engineer with 10 years of experience building scalable SaaS platforms and AI-driven features. I specialize in Next.js, Node.js, TypeScript, and cloud-native deployments, with a strong focus on multi-tenant architectures and production reliability. I have designed end-to-end systems including REST APIs, authentication layers, and Stripe-based subscription billing, and I’ve integrated OpenAI and Anthropic APIs to deliver production-grade AI capabilities in customer-facing products. I thrive on building robust, scalable architectures and collaborating with cross-functional teams to ship high-impact features.

John Langas

Full Stack Developer, Web Developer, Front-End Developer, +2

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I’m John Langas, a Senior Fullstack Engineer with 10 years of experience building scalable SaaS platforms and AI-driven features. I specialize in Next.js, Node.js, TypeScript, and cloud-native deployments, with a strong focus on multi-tenant architectures and production reliability. I have designed end-to-end systems including REST APIs, authentication layers, and Stripe-based subscription billing, and I’ve integrated OpenAI and Anthropic APIs to deliver production-grade AI capabilities in customer-facing products. I thrive on building robust, scalable architectures and collaborating with cross-functional teams to ship high-impact features.…I’m John Langas, a Senior Fullstack Engineer with 10 years of experience building scalable SaaS platforms and AI-driven features. I specialize in Next.js, Node.js, TypeScript, and cloud-native deployments, with a strong focus on multi-tenant architectures and production reliability. I have designed end-to-end systems including REST APIs, authentication layers, and Stripe-based subscription billing, and I’ve integrated OpenAI and Anthropic APIs to deliver production-grade AI capabilities in customer-facing products. I thrive on building robust, scalable architectures and collaborating with cross-functional teams to ship high-impact features.

Available to hire

I’m John Langas, a Senior Fullstack Engineer with 10 years of experience building scalable SaaS platforms and AI-driven features. I specialize in Next.js, Node.js, TypeScript, and cloud-native deployments, with a strong focus on multi-tenant architectures and production reliability.

I have designed end-to-end systems including REST APIs, authentication layers, and Stripe-based subscription billing, and I’ve integrated OpenAI and Anthropic APIs to deliver production-grade AI capabilities in customer-facing products. I thrive on building robust, scalable architectures and collaborating with cross-functional teams to ship high-impact features.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

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Expert

Expert

Expert

Expert

Intermediate

Work Experience

Senior Fullstack Engineer at Weights & Biases

September 1, 2024 - June 1, 2026

Architected and delivered full-stack SaaS features using Next.js, TypeScript, Node.js, and Express, integrating AI APIs to power generative workflows and multi-tenant user experiences across production environments with high reliability and scalability. Implemented Stripe subscription billing with webhooks, customer portal, and plan management flows, ensuring secure payment state synchronization across multi-tenant SaaS environments with consistent financial event processing and auditability. Built RESTful APIs with Node.js and Express, designing scalable service boundaries, authentication flows, and RBAC for admin and user personas in distributed production systems serving enterprise workloads. Developed AI-powered features using OpenAI and Anthropic APIs, including prompt orchestration pipelines, structured outputs, and evaluation loops for improving response quality, reliability, and task-specific accuracy. Designed PostgreSQL and MongoDB schemas for analytics and user data, optimiz

Fullstack Engineer at Unit410

July 1, 2022 - August 1, 2024

Engineered production-grade full-stack SaaS applications using React, TypeScript, Node.js, and Express, focusing on scalable APIs and responsive UI systems supporting enterprise-grade workflows and multi-user platforms. Integrated third-party APIs and authentication systems, implementing OAuth, JWT-based sessions, and secure multi-role access controls across distributed backend services supporting SaaS platform reliability and security. Designed and optimized PostgreSQL database schemas, improving query performance through indexing, normalization strategies, and caching layers for high-traffic workloads and analytics-driven application features. Built reusable frontend components and state management patterns in React, improving developer velocity and ensuring consistent UX across complex dashboards and admin tools used by operational teams. Implemented CI/CD workflows with automated testing and deployment pipelines, reducing release cycles while maintaining high reliability across sta

Software Engineer at Meta

July 1, 2017 - June 1, 2022

Built large-scale distributed frontend systems using React and TypeScript, delivering high-performance user interfaces serving millions of users across global production environments with strict latency and reliability requirements. Developed backend services and APIs in Node.js and internal frameworks, supporting high-throughput data processing, authentication, and real-time feature delivery systems across large-scale infrastructure. Collaborated on data-driven product features using experimentation frameworks, A/B testing pipelines, and analytics instrumentation to measure engagement, performance impact, and user behavior at scale. Optimized application performance through profiling, caching strategies, and reducing render bottlenecks, improving responsiveness across complex web applications with heavy interaction workloads. Implemented secure authentication and authorization systems supporting role-based access and privacy-compliant data handling at enterprise scale across distribut