Senior Full-stack Engineer

About us

Our mission is to reinvent the way people learn, starting with language.

Learning a language can change a life by opening doors to new cultures, careers, and communities. Two billion people around the world are actively trying to learn a language, but the best way to learn (one-on-one tutoring) is hard to access at scale and hasn’t been meaningfully improved in decades. Speak is building a human-level, AI-powered tutor in your pocket: a conversation-first experience that lets learners actually speak, get instant feedback, and progress through carefully designed lessons. The result is a complete path from beginner to confident speaker across multiple languages.

Speak first launched in South Korea in 2019, where Speak has now become the number one language learning app, and we now serve learners across many markets and 15+ languages. Speak is one of the world’s leading AI companies, with over $150m raised in venture investment from OpenAI, Accel, Founders Fund, Khosla Ventures, and more, with a distributed team across San Francisco, Seoul, Tokyo, Taipei, and Ljubljana.

About this role

We’re looking for a Full-stack Technical Lead to drive the next evolution of our growth and marketing experiences. You’ll work across a modern web stack—Next.js, Node.js, and Postgres—to build, optimize, and scale interactive product features that help us acquire and engage users in creative new ways.

As a key member of the Growth Marketing team, you’ll own high-impact initiatives such as user registration, subscription management, and viral campaign experiences. You’ll also guide improvements to our technical architecture and help establish best practices as we modernize a recently migrated Next.js codebase.

What you’ll be doing

• Leading growth-focused projects that drive user excitement and large-scale engagement (e.g. Your Year in Conversation , interactive influencer partnerships)

• Designing and building AI-driven web experiences (e.g. speaking practice with AI Tutor)

• Collaborating closely with cross-functional partners across product, design, and marketing to deliver high-impact initiatives

• Enhancing the architecture, reliability, and development patterns of our full-stack web application through incremental improvements

What we’re looking for?

• 5+ years of experience building high-quality, production-scale web applications, with strong proficiency in React and Node.js

• Ability to balance building the "right way" with shipping quickly when needed

• Enjoyment in iterating rapidly and delivering value through frequent releases

• Excellent communicator who enjoys collaborating across functions

• Nice to have:

  • Deep experience with Next.js

  • Strong knowledge of Postgres and data modeling best practices

  • Familiarity with identity and access domains (authentication, authorization, auditing)

  • Experience with subscription or billing systems

  • Experience deploying and managing applications with Kubernetes

Why work at Speak

1. Join a fantastic, tight-knit team at the right time: we're growing very quickly, we've most recently raised our Series C from some of the top investors in the valley, and we've achieved product-market fit in our initial markets. You'd join at a magical time when a single person could significantly change the course of the company.

2. Do your life's work with people you’ll love working with: we care strongly about our craft and want every person at Speak to feel like they're growing every day. We believe in the idea that working with people you both enjoy and have respect for makes everything better. We hire thoughtfully and only work with people we admire deeply.

3. Global in nature: We're live in over 40 countries and launching in a number of new markets soon. We have dedicated offices in San Francisco, Ljubljana, Seoul, and Tokyo, and you’ll have the opportunity to talk to users in each of these regions on a regular basis as well as travel.

4. Impact people's lives in a major way: Learning a language is one of the single most life-changing skills one can learn, and right now 99% of people never achieve their goal because the process is broken. We’re helping millions of people achieve their goals and improve their lives.

Speak does not discriminate based upon race, religion, color, national origin, gender (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, gender expression, age, status as a protected veteran, status as an individual with a disability, or other applicable legally protected characteristics.