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 senior full-stack engineer to serve as the hands-on technical lead for Discovery, the pod that helps motivated learners and small teams discover, try, and buy Speak. You’ll set technical direction across the web acquisition and purchase journey, including public discovery, authentication, checkout, billing, provisioning, and measurement. You’ll work primarily in TypeScript across Next.js/React, Node.js, and Postgres, partnering with engineers in adjacent pods where the experience crosses team boundaries.

You’ll turn business goals and product requirements into clear technical designs, lead execution across multiple engineers and agent-driven contributions, and raise the bar for architecture, reliability, analytics, and rollout. Near-term work includes self-serve Speak for Business onboarding, web payments experimentation, enterprise-ready web journeys, and foundations that let Marketing publish and measure experiments without depending on engineers for every change.

What you’ll be doing

• Serving as the hands-on technical lead for Discovery, from problem framing and architecture through implementation, launch, and production monitoring

• Designing and building full-stack web journeys that help individuals and small teams find, evaluate, purchase, and start using Speak

• Leading cross-repository integrations across authentication, payments, entitlements, analytics, attribution, CRM, and admin experiences

• Partnering closely with product, design, analytics, Marketing, Sales, and adjacent engineering pods to define scope, sequence dependencies, and deliver end-to-end outcomes

• Setting an enterprise-ready quality bar for privacy and security, payment correctness, observability, performance, and resilient rollouts

• Evolving architecture and development patterns incrementally while protecting conversion and revenue across high-traffic global funnels

• Helping the pod operate AI-natively by reviewing plans and designs before implementation, creating strong QA and verification loops, and enabling AI-assisted contributors to ship safely

• Mentoring engineers and raising the team’s bar for technical judgment, communication, and ownership

What we’re looking for

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

• A track record as the technical lead for ambiguous, multi-system initiatives, while remaining hands-on in architecture and implementation

• Experience designing APIs and backend services, working with relational data, and reasoning clearly about boundaries between systems

• Strong product and business judgment, with the ability to translate growth or B2B objectives into pragmatic scope, measurable outcomes, and durable technical foundations

• Experience building reliable transactional or stateful workflows, with strong instincts around data integrity, idempotency, observability, and safe rollouts

• Ability to balance building the right way with shipping quickly, learning from real usage, and improving systems incrementally

• Excellent cross-functional communication and a desire to mentor engineers and raise the quality of team decisions

• Excitement about AI-assisted development, paired with thoughtful verification and a high production-quality bar

• Nice to have:

  • Deep experience with Next.js and Postgres data modeling

  • Experience with web payments, subscriptions, billing, invoicing, or entitlements

  • Familiarity with identity and access, B2B account models, roles, or provisioning

  • Experience with analytics, attribution, experimentation, CRM, or marketing technology integrations

  • Experience building internationalized web products or working across consumer and B2B SaaS surfaces

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, Tokyo, and Taipei, 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.