Principal Software Engineer - Mend AI (AI Security)

Mend.io; Poland; On-site; PLN 120,000 - 150,000; Full time

Job summary

Mend.io, located in Poland, is seeking a Principal Software Engineer to lead the development of innovative application security solutions utilizing AI technology. This role requires 10+ years in backend software engineering and at least 3 years in a leadership position, driving initiatives in complex environments. As a key decision-maker, you will own architecture and design choices, collaborating with teams to bring impactful solutions to production. The position emphasizes ownership, adaptability, and leveraging AI throughout the software development lifecycle.

Qualifications

• 10+ years of backend software engineering experience.
• 3+ years in a technical leadership role.
• Experience building systems end to end from scratch in a product environment.
• Strong hands-on experience with Go, Java, or Python.
• Solid understanding of cloud environments.

Responsibilities

• Design and build solutions from scratch.
• Leverage AI agents across all stages of development.
• Drive independent research and lead development.
• Act as a technical leader and key decision maker.
• Build and evolve backend architectures.

Skills

Backend software engineering

Technical leadership

System architecture

Modern programming language (Go preferred)

AI integrations

Cloud environments (AWS/GCP/Azure)

Communication skills

Job description

Why Mend.io

We are redefining how modern organizations secure software from open source and custom code to AI-generated components. As the creators of the first AI Native AppSec Platform, we help global enterprises stay safe, fast, and compliant in an era of AI-driven development. Our platform combines intelligent automation, deep risk visibility, and developer-first experiences, shaping the future of application security.

We are also committed to building a collaborative, empowering workplace. If you are excited about this role but do not meet every requirement, we encourage you to apply. Your perspective could be exactly what we need!

Mend.io is looking for a hands‑on Principal Software Engineer (Individual Contributor) to join our Mend AI team, a group building the next generation of application security solutions for AI powered software.

We’re looking for someone who can take end to end ownership of systems, design solid architectures from scratch, and influence both technological decisions and product direction. The right person brings strong experience writing effective, thread‑safe code and building reliable systems in a complex engineering environment.

Our Mend AI product is an innovative solution in AI application security, focused on protecting codebases and systems in the AI era. It helps detect and secure AI/ML components in applications, addressing emerging risks such as data leakage and prompt injection.

This role is a strong fit if you’re excited to independently own and drive innovative projects from research to production. You move fast, leverage AI agents across the development lifecycle, and are comfortable operating in a new and evolving space where standards are still being defined. You take initiative, make decisions, and turn ideas into working solutions quickly.

You’ll work in a fast evolving domain where problems are not fully defined, requiring strong technical judgment, adaptability, and a product oriented mindset. A key part of the role is leveraging AI agents across the development lifecycle from research and design to coding and testing and building hybrid solutions that combine classical algorithms with AI capabilities in a practical, cost effective way.

Responsibilities

• Design and build solutions from scratch, taking full ownership from idea to production
• Develop backend systems, leveraging and customizing AI agents, and extend solutions with simple frontend components when needed
• Leverage AI agents across all stages of development: research, design, coding, and testing to improve speed and quality
• Drive independent research and lead development in new, ambiguous domains, shaping innovative products where standards are still evolving
• Act as a technical leader and key decision maker, owning critical architectural and design choices
• Build and evolve backend architectures, extending traditional microservices with AI/LLM-based capabilities to create advanced security solutions
• Collaborate closely with security researchers, data scientists, and product managers to turn ideas into production ready solutions

Requirements

• 10+ years of backend software engineering experience
• 3+ years in a hands on technical leadership role (Principal / Tech Lead / Architect)
• Strong experience building systems end to end from scratch in a product environment
• Strong hands on experience with a modern programming language (Go preferred; experience with Java or Python is also valuable), and the ability to quickly adapt to new languages and technologies
• Strong product mindset and ability to connect technical decisions to business impact
• Proven ability to own and drive initiatives independently in ambiguous environments
• Experience building or working on systems that integrate AI/LLM based capabilities into real world applications
• Hands on experience using AI agents throughout the development lifecycle, with a deep understanding of their strengths, limitations, and best practices
• Solid understanding of cloud environments and modern development practices (AWS/GCP/Azure)
• Strong communication skills and ability to collaborate effectively with senior stakeholders

Nice to Have

• Hands on experience developing, tuning, or customizing LLM based solutions (beyond using out of the box APIs)
• Familiarity with AI security challenges (e.g., prompt injection, model leakage, adversarial attacks)
• Experience with machine learning workflows (training, deployment, inference)
• Experience with tools such as LangChain, Hugging Face, or OpenAI SDKs
• Background in application security, cloud security, or DevSecOps

Our Culture

At Mend.io, we are leading the way in securing AI-powered applications, and we believe the best innovations come from teams where everyone feels valued. We are committed to a workplace built on respect, trust, and growth, where learning and flexibility empower people to do their best work.