June 1, 2026

Senior Software Engineer

Senior • Hybrid

20,800 - 25,900 PLN/mo

Krakow, Poland

Upside is a software consultancy built by engineers, for engineers. We partner with global companies to solve real, complex technical challenges. We’re deep into Applied AI and R&D, building both production-grade platforms for clients and our own open-source tools like Enthusiast (Agentic AI framework).

We operate in a Forward-Deployed model. We don’t sit behind a wall of specs or wait for the tickets. We get into the trenches with the client, identify the actual challenges, and take full ownership of the solution. Our teams are small (3–9 people), autonomous, and cross-functional.

What it means for you

You'll work with a capable and driven team, and partner directly with senior business leaders on technical decisions, shaping systems - not just implementing them. You’ll have the autonomy to choose the right tools and the ownership to ensure the architecture performs under pressure.Your focus stays where it counts: mission-critical logic and high-impact experiments, not repetitive tasks and countless meetings.

You’ll contribute to strategic open-source projects and build AI-driven solutions.

Role Overview

As a Senior Backend Engineer, you’ll be the backbone of our development efforts and a key driver of our engineering culture. You will design, build, and scale resilient systems for international clients while staying close to the code. We’re looking for someone who brings ready solutions rather than problems to solve, and treats the client’s product as their own. This isn't a short-term opportunity  - we’re looking for a partner to grow with us, someone who thrives in a highly collaborative environment and proactively shares "lessons learned" to level up the entire team.

Responsibilities

  • Drive technical direction: Own the architecture and implementation of complex backend systems.

  • Problem Solving: Identify systemic risks before they manifest and propose clear, actionable ways to bypass them.

  • Consulting: Work directly with stakeholders to translate business needs into scalable technology.

  • Mentorship: Share your observations and "lessons learned" to help the whole team level up.

  • AI Integration: Identify where Applied AI can actually improve a product and lead the implementation.

Requirements

  • Experience: 5+ years of building web applications (preferably in Python frameworks).

  • Background: Completed university degree in computer science, data science or similar field 

  • Architecture: Deep understanding of monoliths, microservices, and messaging patterns.

  • Databases: Expert knowledge of PostgreSQL and performance optimization at scale.

  • Infrastructure: Practical experience with CI/CD, Docker, and AWS/GCP.

  • Mindset: Proactive, technology-driven, and ready to experiment.

  • AI-Native: You use tools like Claude or Cursor to move faster.

  • English: Fluent (C1) for direct client collaboration.

Our Tech Stack: Python, PostgreSQL, AWS, Docker, Kubernetes. Ruby is present in some of our projects but we are Python first. 

Value Proposition

  • Built for the long run  We hire for the company, not just a project - looking for passion driven engineers who want to grow with Upside over time

  • Small teams, real accountability. 3-9 people per engagement. We're small by design. That means your decisions carry weight and you are visible.

  • Mission-critical work: We handle complex  projects that move the needle for international brands. Our clients are scaling companies, established international brands, and large institutions. The systems you build will be under real load, with real stakes.

  • Real Ownership: You take part in the decision making process on technology and implementation..You’re empowered to take initiative, experiment, and drive solutions that create real impact.

  • No Micromanagement: We trust you to own your work and deliver outcomes - no unnecessary oversight.  

  • Collaborative R&D: Contribute to targeted Open-source projects and internal AI research.

  • Growth through challenges: Complex problems and direct client exposure means you’ll grow by action.

  • Applied AI as a first-class discipline. We don't bolt AI onto projects as an afterthought. You'll identify where it genuinely moves the needle and lead the implementation - on client work and on our own open-source tooling.

  • The tools you want, without the approval process. If something makes you faster or sharper, we want you using it.

  • Transparent progression path. We have defined engineering levels with clear criteria - you'll know exactly what each role looks like, and what it takes to get from one to the other. No ambiguity, no waiting for someone above you to move on.

Compensation & Location

  • Location: On-site in Kraków; Hybrid; remote from anywhere in Poland with regular team on-sites.

  • Salary:
    Senior Engineer: 20 800 - 25 900 PLN net + VAT
    Lead Engineer: >26 500 PLN net + VAT

If you’d like to understand more about how we work or read about the recruitment process in detail, feel free to explore our handbook. If something important to you isn’t mentioned - share your thoughts with as at careers@upsidelab.io

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Wroclaw, Poland

130,000 - 190,000 USD/yr

🏢 Summary: Senior or Staff Backend Engineer role focused on architecting and scaling AI-native backend systems for a modern accounting platform. The position involves designing distributed services, building high-performance APIs, and establishing engineering standards to support rapid, reliable product delivery. You will work closely with Product, AI, and Operations teams to develop agentic systems and scalable data pipelines. 🗂️ Requirements: 5–10+ years of backend engineering experience, Proven experience designing, building, and operating production backend systems at scale, Strong expertise in API design, Strong expertise in data modelling, Deep understanding of distributed systems trade-offs, Hands-on experience with AWS or GCP in production, Practical experience with CI/CD in high-frequency deployment environments, Experience implementing testing and deployment strategies, Strong knowledge of observability practices, Experience participating in on-call rotations 📃 Skills: TypeScript, Node.js, React, AWS, GCP, Terraform, PostgreSQL, OpenAI, Azure, CI/CD, APIs, DistributedSystems 🏢 Description: ABOUT THE ROLE We're looking for a Senior or Staff Backend Engineer to own and evolve our backend services as we scale. This is a broad, high-impact role — you'll architect new features, build the systems that underpin our core product, and set the engineering standards that shape how the whole team works. The focus is on building a modern, AI-native developer experience. That means working closely with Product, AI, and Operations teams to design agentic systems, distributed data pipelines, and scalable incident response infrastructure — and doing it in a way that lets the team ship with confidence multiple times a day. WHAT YOU'LL WORK ON Architecture and feature design Partner with Product, AI, and Operations teams to architect new features and complex agentic systems. Make clear architectural trade-offs that balance platform, product, and business goals. Backend services and APIs Build and maintain the backend services and APIs that power the core product. Ensure systems are secure, well-tested, and high performance. Distributed systems Design and implement distributed services to orchestrate data pipelines, automate investigations, and enable incident response at scale. Operational excellence Own operational best practices so the team can ship multiple times a day with confidence. Healthy on-call culture and strong observability are part of what you'll build and maintain. Engineering standards Set the bar for writing, communication, and system design across the team. Your influence will shape how a modern AI-native product is built. WHAT WE LOOK FOR 5–10+ years of backend engineering experience A strong track record designing, building, and operating production backend systems at scale. Deep backend fundamentals Expertise in API design, data modelling, and reasoning about distributed systems trade-offs. You understand the nuances, not just the patterns. AWS or GCP hands-on experience Solid understanding of how infrastructure decisions impact application reliability and performance. You've run things in production, not just designed them. CI/CD in practice Practical experience with testing and deployment strategies in high-frequency shipping environments. Observability and on-call maturity A solid grasp of what good observability looks like and how to build healthy on-call practices that don't burn people out. Bonus Experience at an early-stage or scaling startup. Exposure to modern AI and ML systems. Experience shipping product without a dedicated product manager. TECH STACK TypeScript, React, Node.js, AWS, Terraform, PostgreSQL, OpenAI, Azure AI. The team uses GitHub, Slack, Linear, Figma, and Notion day to day. THE TEAM Small, senior, and in-person. The office is in central Wrocław, next to the main train station. The expectation is 4–5 days a week in the office. Relocation support is available for the right candidate. COMPENSATION & BENEFITS Salary $130,000 – $190,000 USD depending on experience, plus competitive equity. Wellness and commute stipend $100 per month. Hardware Premium hardware provided — MacBook Pro and AirPods. Food Daily in-office lunch and dinner. Time off 20 PTO days plus 9 US public holidays. Relocation Support available for candidates relocating to Wrocław.

Technology

TechTree

Senior/Staff Backend Engineer

Senior

On-site

Wroclaw, Poland

130,000 - 190,000 USD/yr

🏢 Summary: Senior or Staff Backend Engineer role focused on architecting and scaling AI-native backend services for a modern accounting platform. The position involves designing distributed systems, building secure and high-performance APIs, and establishing engineering standards to support rapid, reliable product delivery. You will work closely with Product, AI, and Operations teams to build scalable data pipelines and incident response infrastructure. 🗂️ Requirements: 5–10+ years of backend engineering experience, Proven experience designing and operating production backend systems at scale, Strong expertise in API design and data modelling, Deep understanding of distributed systems and architectural trade-offs, Hands-on experience with AWS or GCP in production environments, Practical experience with CI/CD pipelines and automated testing, Experience building and maintaining observability and on-call practices 📃 Skills: TypeScript, Node.js, React, AWS, GCP, Terraform, PostgreSQL, OpenAI, Azure, CI/CD, APIs, DistributedSystems, DataModelling, Observability 🏢 Description: ABOUT THE COMPANY We're an applied AI company building an AI-native alternative to legacy accounting software — a market worth tens of billions in annual recurring revenue. Our mission is to help entrepreneurs focus on what matters in their business and life, and to help their accountants become more strategic. We've raised $20M from a group of top-tier investors and have grown ARR 60% month-on-month since our public launch. We now serve thousands of businesses and are expanding our product to serve accountants directly — creating a two-sided platform where both business owners and their accountants use and recommend us. We're at an early but proven stage, moving fast, and building a world-class engineering team in Wrocław to match our ambition. ABOUT THE ROLE We're looking for a Senior or Staff Backend Engineer to own and evolve our backend services as we scale. This is a broad, high-impact role — you'll architect new features, build the systems that underpin our core product, and set the engineering standards that shape how the whole team works. The focus is on building a modern, AI-native developer experience. That means working closely with Product, AI, and Operations teams to design agentic systems, distributed data pipelines, and scalable incident response infrastructure — and doing it in a way that lets the team ship with confidence multiple times a day. WHAT YOU'LL WORK ON Architecture and feature design Partner with Product, AI, and Operations teams to architect new features and complex agentic systems. Make clear architectural trade-offs that balance platform, product, and business goals. Backend services and APIs Build and maintain the backend services and APIs that power the core product. Ensure systems are secure, well-tested, and high performance. Distributed systems Design and implement distributed services to orchestrate data pipelines, automate investigations, and enable incident response at scale. Operational excellence Own operational best practices so the team can ship multiple times a day with confidence. Healthy on-call culture and strong observability are part of what you'll build and maintain. Engineering standards Set the bar for writing, communication, and system design across the team. Your influence will shape how a modern AI-native product is built. WHAT WE LOOK FOR 5–10+ years of backend engineering experience A strong track record designing, building, and operating production backend systems at scale. Deep backend fundamentals Expertise in API design, data modelling, and reasoning about distributed systems trade-offs. You understand the nuances, not just the patterns. AWS or GCP hands-on experience Solid understanding of how infrastructure decisions impact application reliability and performance. You've run things in production, not just designed them. CI/CD in practice Practical experience with testing and deployment strategies in high-frequency shipping environments. Observability and on-call maturity A solid grasp of what good observability looks like and how to build healthy on-call practices that don't burn people out. Bonus Experience at an early-stage or scaling startup. Exposure to modern AI and ML systems. Experience shipping product without a dedicated product manager. TECH STACK TypeScript, React, Node.js, AWS, Terraform, PostgreSQL, OpenAI, Azure AI. The team uses GitHub, Slack, Linear, Figma, and Notion day to day. THE TEAM Small, senior, and in-person. The office is in central Wrocław, next to the main train station. The expectation is 4–5 days a week in the office — this is a deliberate choice, not a compromise. Relocation support is available for the right candidate. COMPENSATION & BENEFITS Salary $130,000 – $190,000 USD depending on experience, plus competitive equity. Wellness and commute stipend $100 per month. Hardware Premium hardware provided — MacBook Pro and AirPods. Food Daily in-office lunch and dinner. Time off 20 PTO days plus 9 US public holidays. Relocation Support available for candidates relocating to Wrocław.

Technology

Backbase

Senior AI Applied Software Engineer (Fullstack)

Senior

Hybrid

Krakow, Poland

20,000 - 24,000 PLN

🏢 Summary: Senior AI Applied Software Engineer role focused on designing and delivering secure, scalable digital banking features within the Entitlements domain (Access Control, Approvals, Limits). The position combines backend and frontend engineering with AI innovation, contributing to LLM-based voice assistants and real-time personalization engines. You will lead full SDLC, shape architecture across microservices and APIs, and mentor engineers while building high-traffic fintech products. 🗂️ Requirements: 5–7+ years of experience building complex, high-traffic products, Strong Java and Spring JPA/Hibernate expertise, Experience with Maven and microservices architecture, Cloud technologies experience, Strong Angular and TypeScript skills, Proficiency with RxJS, Experience with Webpack and Jenkins, Solid knowledge of Enterprise Integration Patterns, Ability to design scalable systems handling complex data flows, Experience optimizing CI/CD pipelines, Excellent English communication skills, Residence in Kraków area and hybrid availability (2 days onsite) 📃 Skills: Java, Spring, JPA, Hibernate, Maven, Microservices, Cloud, Angular, TypeScript, RxJS, Webpack, Jenkins, Vue.js, OpenAI, ML, CI/CD, APIs 🏢 Description: The Job At Backbase, we don’t just deliver software – we redefine how people manage their finances. We are looking for a Senior AI Applied Software Engineer to join our R&D department in Kraków. You will join the team which sits at the core of Backbase platform: Entitlements. Handling complex problems related to Access Control, Approvals and Limits. By joining our team, you won’t just write code; you will design systems that impact millions of users across over 100 financial institutions worldwide. Meet the Job As a Senior AI Applied Software Engineer  you are a technical cornerstone of your squad. You will design and deliver complex features with minimal guidance, ensuring that both the "engine" (Backend) and the "experience" (Frontend) are performant, secure, and scalable. Full SDLC Ownership: Lead the entire lifecycle of digital banking products—from initial idea and architectural design to release and maintenance. Architectural Excellence: Improve system architecture and design components that integrate smoothly across APIs and microservices. Technical Leadership: Act as a go-to resource for your team, mentoring junior engineers, conducting critical code reviews, and raising the bar for engineering standards. AI & Innovation: Contribute to the evolution of LLM-based voice assistants and real-time personalization engines using OpenAI and ML models. Security-First Mindset: Implement "Entitlements" and fraud prevention services with a focus on non-functional requirements like security, scalability, and resilience. Collaborative Culture: Work in a Pod based model, collaborating with Architects, Product Owners, and UX Designers to align technical solutions with business needs. Who You Are Location: You live in Kraków or nearby area and you are willing to work in a hybrid mode - twice per week from our office. Experience: You have 5–7+ years of professional experience building complex, high-traffic products. Backend Mastery: Solid understanding of Java , Spring JPA/Hibernate , and Maven . Experience with Microservices (Netflix OSS is a plus) and Cloud technologies. Frontend Expertise: Strong skills in Angular and TypeScript . You are proficient with RxJS and modern build systems (Webpack, Jenkins). Experience with Vue.js is a plus. System Design: You have a solid grasp of Enterprise Integration Patterns and can design systems that handle complex data flows between services. The "Senior" Edge: You don't just solve tickets; you identify gaps in tooling, reduce technical debt, and optimize CI/CD pipelines to streamline delivery. Communication: Excellent English (spoken and written). You can confidently explain technical concepts to non-technical stakeholders and get buy-in for your architectural decisions. Domain Knowledge: Previous experience in Fintech or Banking is highly considered an advantage. What We Offer Growth: €1,000 annual self-development budget, a clear promotion path, and dedicated time for training. Rewards: Competitive base salary plus an annual bonus and referral bonuses. Hybrid Work: A flexible arrangement combining remote work with our vibrant Kraków office. Office Perks: Daily lunches, community breakfasts on Wednesdays, and high-end hardware (MacBook). Well-being: Private healthcare (Luxmed), Headspace app subscription, and a Work-From-Home allowance. Culture: Integration events, flexible working hours, and a focus on healthy work-life balance.

Technology

RemoDevs

Senior Backend Python Developer

Senior

On-site

Warsaw, Poland

7,000 - 9,000 USD

🏢 Summary: Senior Backend Engineer role focused on designing, building, and maintaining production backend systems and AI-driven workflows in a fully onsite Warsaw office environment. The position involves ownership of system architecture, APIs, distributed systems, and cloud infrastructure from design through production. Candidates will collaborate across teams, improve engineering processes with AI tools, and contribute to scalable, reliable solutions. 🗂️ Requirements: Strong experience as a senior backend engineer on production systems, Excellent Python programming skills, Understanding of distributed systems, Experience with AWS or Azure cloud platforms, Knowledge of SQL and NoSQL databases, Experience with asynchronous processing and service design, Ability to design and deliver systems from idea to production, Strong written and spoken communication skills, Regular use of AI development tools, Ability to work fully onsite in Warsaw 📃 Skills: Python, AWS, Azure, SQL, NoSQL, APIs, AI, TypeScript, GitHub, Copilot, Claude, OpenAI, Codex 🏢 Description: Please note: This role requires working from our office in Warsaw city centre 5 days a week . This is a fully on-site position , and remote or hybrid work is not available . About Us Many companies want to use AI agents, but these agents often struggle with real business tasks. We solve this problem by building a platform that helps AI understand business rules, workflows, and processes. This allows AI to make better decisions and provide accurate, reliable, and compliant results. Well-known companies from different industries use our technology to automate up to 85% of customer cases, reduce handling time by 20–25%, and complete tasks that used to take hours in just seconds. We also work with leading technology partners and have been recognized for our innovative approach. Our goal is to help people everywhere get better answers through AI. Job Description We are looking for a Senior Backend Engineer who can take ownership of important systems instead of only completing assigned tasks. You will solve complex problems, design backend solutions, build them, and make sure they run well in production. We want someone with strong technical skills, good communication, and the ability to create simple, reliable, and easy-to-maintain systems. This is a product engineering role with responsibility from system design to production. The position is based in Warsaw and requires office work. Responsibilities Design and develop backend services, APIs, data processing, and background tasks for production systems. Turn unclear business needs into clear technical plans and practical solutions. Maintain services after release by improving reliability, monitoring, performance, and fixing issues. Make good decisions about system architecture, data models, interfaces, and future scaling. Write technical documentation, architecture notes, and diagrams when they help the team. Work closely with product managers, frontend engineers, and platform engineers to deliver complete solutions. Improve development processes using AI tools, automation, and internal workflows. Support the team through code reviews, design reviews, and practical technical leadership. Requirements Strong experience as a senior backend engineer working on production systems. Excellent Python skills and the ability to write clean and maintainable code. Good understanding of distributed systems, including concurrency, failure handling, data consistency, asynchronous processing, and service design. Experience with cloud platforms such as AWS, Azure, or similar services. Knowledge of SQL, NoSQL databases, schema design, and performance optimization. Ability to take a project from an idea through design and implementation to production. Strong written and spoken communication skills with the ability to explain technical topics clearly. Regular use of AI tools in everyday development and interest in improving AI-based workflows. Nice to Have Experience with LLM-based applications, search systems, AI infrastructure, or large data pipelines. Knowledge of TypeScript or the ability to contribute to frontend development when needed. Experience guiding other engineers and influencing technical decisions without being a formal manager. What We Offer B2B contract and company stock options. MacBook Pro for work. Modern technology stack and opportunities to contribute to open-source projects. Access to advanced AI development tools, including GitHub Copilot, Claude Code, OpenAI Codex, TypingMind, and MCP servers. Our Culture and Values Our leadership team has strong experience in AI and knowledge management. We have secured more than $60 million in funding and achieved three years of continuous 3x growth. Our work is based on these values: Quality – We aim for excellent work and high coding standards. Momentum – We take initiative and keep projects moving forward. Accountability – We take responsibility and give honest, respectful feedback. Hard Work – We believe great results come from teamwork and consistent effort. Learning Agility – We stay curious, learn from mistakes, and improve every day. Adapt and Thrive – We accept change and see challenges as opportunities. Win Together – We succeed as one team through honesty, openness, and support for our shared mission.