Senior/Software Engineer II, Backend

Our mission at Duolingo is to develop the best education in the world and make it universally available. It’s a big mission, and that’s where you come in!

At Duolingo, you’ll join a team that cares about finding innovative solutions to complex technical problems, running countless experiments (300+ at a time!) with our massive user base to make data-driven decisions, and educating our users and employees alike. You’ll have limitless learning opportunities, mentorship and collaboration with world-class minds, and a variety of projects with large scopes — while doing work that’s both fun and meaningful. 

Join our life-changing mission to develop education for our half a billion (and growing!) learners around the world.

We’re looking for backend engineers who have experience building and operating reliable, scalable systems. Your background may be in product engineering, infrastructure, platform engineering, or a combination of these. What matters most is strong backend fundamentals, sound systems thinking, and the ability to take ownership of complex technical problems from design through production.

Below you can find more information about the team we're hiring for:

Duolingo Score:

Duolingo Score is how we reflect a learner's real language proficiency back to them. As a backend engineer on this small, high-impact team, you'll help make learners care about their score as much as they care about their streak. You'll partner closely with the Score Pillar's product and design team and our iOS and Android engineers, working on the systems that power score calculation, proficiency modeling, and how score surfaces across the app — including integrations with external platforms like LinkedIn, so learners can showcase their proficiency beyond Duolingo.

Ads:

Duolingo's Monetization pillar builds the systems that fund our mission — from subscription packaging and advertising to ML-powered personalization. As a Backend Engineer on the Ads team, you'll work on a product engineering team responsible for growing and scaling Duolingo's ads business: high-quality ads that delight learners, fit seamlessly into the product experience, and meaningfully contribute to our bottom line. The team owns ad serving, mediation and demand, in-product ad formats and surfaces, and more. You'll work cross-functionally with product, design, data science, machine learning, and ad operations.

Observability:

The Observability team builds infrastructure and tools that give engineers confidence and clarity at Duolingo scale. We create monitoring, alerting, and debugging experiences that help teams ship faster and respond to incidents effectively. In this team, you'll build instrumentation frameworks, deploy telemetry infrastructure, design dashboards, and connect signals to catch issues before they impact learners. We're looking for engineers passionate about developer experience and reliability.

AI Platform:

As a member of the AI Tooling and Ecosystem Team, you will be responsible for developing and maintaining tools and services that power Duolingo's use of AI in the product. You will design systems for managing datasets, evaluating the performance of AI models, and building AI workflows. You will help shape how Duolingo builds features using AI, enabling teams to easily define quality metrics, combine human and AI feedback, and compare model performance across different use cases.

🧠  You will...

• Collaborate on software projects with product design and backend aspects
• Develop, release, and maintain backend services and/or infrastructure
• Lead individual project priorities, milestones, and ensure we're always shipping

✅  You have...

• A Bachelor’s degree in Computer Science or a related technical field
• Strong competencies in data structures, algorithms, and software design
• Experience programming in Java, Python, or Kotlin
• Solid understanding of one or more database technologies

⭐  Exceptional candidates will have...

• Industry experience building high-traffic APIs using public cloud providers
• Experience with industry observability technology, such as OpenTelemetry, Grafana, Prometheus, or DataDog.