Staff / Senior Staff Software Engineer – AI Systems
At ButterCMS · Warsaw, Mazowieckie, Poland
Salary: PLN 32,000–40,000 a month
- Engineering
- Full-time
- Staff or principal
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Open to Poland
“Warsaw, Mazowieckie, Poland”
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- Posted
- 14 October 2026
- First seen by us
- 15 October 2026
- Last checked
- 12 hours ago
Job description
From ButterCMS’s job post, as they wrote it.
CKSource builds CKEditor, an open-source rich text editor used by millions worldwide. We're part of Tiugo Technologies, alongside TinyMCE, ButterCMS, and Uploadcare.
Your role:
We're looking for a hands-on Staff / Senior Staff Software Engineer to drive the architecture and technical direction of backend of AI-powered systems in CKEditor.
CKEditor AI is already in production, with features like AI Chat, Quick Actions, and Review. We're expanding our AI platform, integrating LLMs, contextual data, APIs, and external systems.
Read the full description
This is an individual contributor role, not an ML research or people-management position. You'll combine strong software engineering fundamentals with the challenges of building reliable, scalable AI-powered products.
Key Responsibilities:
* Lead the architecture and technical direction of AI-powered systems, from early exploration to production and beyond.
* Design scalable, maintainable systems, making sound decisions about APIs, service boundaries, reliability, performance, security, and cost.
* Turn complex product ideas into experiments, prototypes, and production-ready solutions.
* Build reliable LLM integrations and establish practices for testing, evaluation, monitoring, and improving AI features.
* Stay hands-on by writing and reviewing code, solving complex technical challenges, and mentoring engineers.
* Influence engineering practices and help teams adopt AI development tools without compromising code quality or maintainability.
To be successful in this role you need the following:
* Proven experience designing and delivering complex production systems at Staff, Senior Staff, Tech Lead, or equivalent level.
* Strong hands-on experience with TypeScript, Node.js, software architecture, and distributed systems.
* Experience building LLM- or AI-powered features in production, including testing, evaluation, observability, and reliability.
* Strong architectural judgment and the ability to balance simplicity, scalability, and long-term maintainability.
* End-to-end ownership, from ambiguous technical challenges to successful production delivery.
* Ability to influence technical decisions, mentor engineers, and collaborate effectively across teams without formal authority.
Nice to have:
* Multi-provider LLM integrations, AI evaluation frameworks, tracing, or experimentation.
* AWS, infrastructure as code, and event-driven architectures.
* Experience building developer platforms, APIs, SDKs, or open-source products.
* Experience creating shared libraries, frameworks, or internal platforms.
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 32.000 - 40.000 PLN + VAT (or its equivalent on the employment contract) - the final level and compensation will depend on your experience, technical expertise, and the scope of your previous responsibilities.
* 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, PZU or Medicover) and Multisport card.
* 2 weeks of paid parental leave for our contractors.
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