Senior Software Engineer

We are the company that stands behind the spectacular success of CKEditor, used by millions of people around the world. At CKSource we produce software components that other developers use to build their applications (WYSIWYG editor, file manager, document converters, etc.). Our flagship product is CKEditor 5 – an open-source, modern JavaScript (soon TypeScript) rich text editor with custom data model and virtual DOM – check our GitHub repository.

We are part of Tiugo Technologies, a launchpad for new developer platforms, helping software companies accelerate growth, increase operating efficiency, and scale their business. Tiugo contains a suite of brands that are API-first, market-leading developer platforms focused on content creation and digital collaboration. Tiugo’s current family of brands includes CKEditor, TinyMCE, ButterCMS, and Uploadcare.

Together our products have powered millions of software applications and websites. Enabling content and communication in everything from Microsoft to NASA, you might not know our name, but you’ve probably used our software.

Your role:

As a Senior Software Engineer on our AI team, you will play a key role in building and evolving the backend services that power AI capabilities in CKEditor 5. This is a unique opportunity to work at the intersection of AI and content creation — where LLMs meet their most natural application: text processing. You will design, build, and maintain services that integrate with leading LLM providers such as OpenAI, Anthropic, and Google Gemini, enabling features like contextual text suggestions, automated content generation, and other intelligent editing experiences used by millions of users worldwide.Working closely with other engineers, you will contribute to developing scalable backend systems, experimenting with new AI-driven capabilities, and delivering production-ready solutions that enhance how people create and interact with digital content.Want to see what we've built so far? Check out our AI features in action at https://ckeditor.com/ckeditor-5/demo/ai and imagine where you could take them next.Our core stack is TypeScript and Node.js. We're looking for an experienced backend engineer with curiosity about AI — someone who can balance innovation with production-grade quality and help shape how we build AI-powered features.

Key Responsibilities:

• Design, build, and maintain backend services that power AI features for CKEditor 5 — including API orchestration, streaming, event-driven processing, and data persistence.

• Integrate and orchestrate LLM providers to deliver intelligent editing features such as contextual text suggestions, automated content generation, and other intelligent text processing capabilities.

• Engage in code reviews, pair programming, and cross-functional collaboration to ensure the highest quality results.

• Write clean, maintainable, and well-structured code, balancing readability with appropriate documentation.

• Share best practices on programming standards, tools, and processes to foster continuous improvement.

  
  

To be successful in this role you need the following:

• Over 5 years of software development experience.

• Strong proficiency in TypeScript and Node.js.

• Experience building and maintaining backend services - REST APIs, relational databases (PostgreSQL), message queues, Docker.

• Curiosity about AI/LLMs and willingness to work with them daily.

• Excellent problem-solving skills and the ability to think critically and creatively.

• Outstanding communication skills, both verbal and written.

  
  

Nice to have:

• Hands-on experience integrating LLM APIs (OpenAI, Anthropic, Google, or similar).

• Understanding of prompt engineering, function/tool calling, and streaming.

• Experience with event-driven architectures (SQS/SNS or similar).

• Familiarity with observability tools (OpenTelemetry, tracing).

  
  

Why join CKSource:

Our people are a huge part of what makes CKSource a great place to work! Aside from a great team, some of our benefits include:

• B2B contract-based monthly remuneration is 24.000 - 32.000 PLN + VAT or its equivalent on the employment contract.

• Quarterly and annual financial bonuses depending on the company’s performance.

• Flexible schedule and the possibility to work fully remotely.

• Professional development resources (up to 5 days of additional leave and 6 000 PLN yearly).

• LinkedIn Learning access.

• Extra leave for Tiugo Day - our company’s foundation day and your birthday.

• English lessons with a native speaker and an online language platform where you can learn English, Spanish, and German.

• Access to a mental health and well-being platform with 24/7 dedicated psychological support.

• Private medical care (Enel Med or Medicover) and Multisport card.

• 2 weeks of paid parental leave for our contractors.

  
  

Recruitment process

• HR interview.

• Technical interview with Jacek Bogdański (Engineering Manager).

• Interview with Bartek Czerwonka (Senior Director of Engineering).