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Senior Backend Engineer C# | API & Client Libraries

RemoteCologne, Nordrhein-Westfalen, GermanyEngineering

Meet DeepL

DeepL, Europe's leading AI company since 2017, is dedicated to breaking down language barriers and bringing cultures closer together. Our expertise in AI and neural networks has enabled us to create cutting-edge communication technologies for businesses, including the acclaimed DeepL Translator which offers 30+ languages, and DeepL Write, our AI writing companion. Our core offering includes a suite of products and tools made for businesses to communicate more effectively, both internally and with their customers around the globe.

Our goal is to become the global leader in Language AI and build products that help drive better communication, drive connection, and make real-life impact. To do that, we need talented people, like you, who want to be a part of this exciting journey. If you're ready to work with a dynamic team and build your career in the fast-moving AI space, DeepL is your next destination.

What sets us apart

We are committed to innovation and to a nurturing work environment. Founded by developers and researchers, we spend a lot of time actively reviewing the latest trends in generative AI and software engineering. Known for pioneering AI technologies, we dive deep into cutting-edge research to create not only translations, but advanced language solutions. Combining our use of modern technology, comprehensive employee benefits with our open and welcoming work culture is what sets us apart.

When we tell people about DeepL as an employer, the reactions are overwhelmingly positive. Maybe it's because of the products that have helped countless people worldwide, or maybe it's because of our shared goal of improving communication for individuals and businesses worldwide. What we're certain of is this: being part of DeepL means joining a team committed to innovation and the well-being of its employees.

Meet the team behind this journey

Thanks to our unique neural networks, DeepL is able to deliver the world’s best translation quality. Many thousands of users use our API to bring our translations into their applications, translating billions of characters per month. To make our AI easy to use, we provide open source libraries in a wide range of programming languages - to date we have released client libraries for Python, .NET, Node.js, PHP, and Java. You can find more on our GitHub:

You will contribute to our backend services (C#, ASP.NET Core), adding exciting new API features. You will also develop our client libraries and make sure that they deliver value to the developer community. You can expect to work in a highly experienced cross-functional team, with frequent code reviews and a focus on high quality.


Your responsibilities

  • Design, implement and maintain new features for the DeepL API on our backend services, collaborating with multiple engineering teams
  • Develop and maintain open-source client libraries for the DeepL API in several programming languages
  • Contribute to monitoring the API services in production, e.g. by defining expressive metrics and ensuring informative logs

Qualities we look for

  • Strong proficiency in backend software development with C# and ASP.NET Core
  • Experience with the design of Web APIs
  • Solid understanding of algorithmic complexity and common data structures
  • Effective and pragmatic; you can weigh between 'perfect' and 'good enough' depending on priorities and business impact
  • The ability to explain complex ideas and designs to developers with a wide variety of experience and backgrounds
  • Fluent in English, knowledge of other languages is a plus

We'd especially love to talk if you have any of the following:

  • Experience developing services for public API products
  • Experience maintaining open-source projects
  • Significant experience in multiple programming languages

What we offer

- Diverse and internationally distributed team: joining our team means becoming part of a large, global community with people of more than 90 nationalities. We're more than just colleagues; we're a group of professionals with a shared mission to connect diverse cultures. Our global presence is growing–we've doubled in size nearly every year, with our employees based in the UK, Germany, the Netherlands, Poland, the US, and Japan, and we continue to expand our network.

- Open communication, regular feedback: as a language-focused company, we value the importance of clear, honest communication. We value smooth collaboration, direct and actionable feedback, and believe that leading with empathy makes us better together.

- Remote work, flexible hours: whether you're near or in our hubs in cities like Cologne, Berlin, Amsterdam, London, or prefer the comfort of your own home, you decide where your office is. We offer remote opportunities, flexible working hours and trust in your productivity, all in sync with your team's general locations and time zones to foster effective and seamless collaboration. Our aim is to integrate your work with your lifestyle, ensuring a balance that respects both your needs and our operational requirements.

- Regular in-person team events: we bond over vibrant events that are as unique as our team, from local team and business unit gatherings, to new-joiner onboardings, to company-wide events that bring us all together–literally.

- Monthly full-day hacking sessions: every month, we have Hack Fridays, where you can spend your time diving into a project you're passionate about and get the opportunity to work with other teams–we value your initiatives, impact, and creativity.

- Comprehensive health insurance: your health comes first. With our comprehensive insurance, we'll make sure you're covered from head to toe.

- 30 days of annual leave: we value your peace of mind. With 30 days off (excluding public holidays) and access to mental health resources, we make sure you're as strong mentally as you are professionally.

- Annual learning budget: because we never stop learning, we’ve set up an annual budget for your professional development—pick a learning path which contributes to your career development and we'll back you up.

If this role and our mission resonate with you, but you're hesitant because you don't check all the boxes, don't let that hold you back. At DeepL, it's all about the value you bring and the growth we can foster together. Go ahead, apply—let's discover your potential together. We can't wait to meet you!

Please make sure to send your application in English.