Senior Backend Engineer Job San Francisco area,California USA,Software Development

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 are looking for a senior backend focused but full‑stack capable engineer to work on building novel AI‑powered product experiences. The ideal candidate will have experience working in close coordination with product, design, and machine learning teams, as well as have a background in building polished consumer applications. This role sits at the center of developing our newest products focused on programmatic, conversationally‑driven language learning and will be an instrumental contributor to the future of our company.

What

you'll be doing

Building novel AI‑driven product experiences and user interfaces on the web
Full‑stack engineering, but focused on creating scalable backend systems.
Debugging complex streaming issues.
Owning the entire development cycle of features, from conception to production
You’ll be able to write code very quickly, ship frequently, and make a huge impact on our business by helping us scale our content

What we're looking for

5+ years of industry experience working as a Backend Engineer, preferably in a fast‑paced startup environment
- bonus: worked on an app that has been used by 1M users
Excellent problem‑solving and communication skills, and the ability to work independently or as part of a team
Coach and mentor other engineers
Strong product sense: ability to think broadly/cross‑functionally about product experiences

Why work at Speak

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.

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.

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.

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.

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