Senior Backend Engineer

Alcor; Warszawa; On-site; PLN 180,000 - 300,000; Full time

Job summary

Qlub is seeking a Senior Backend Engineer – Payments to design, build, and operate secure, scalable payment services across gateways, transactions, and integrations with POS systems and providers. You’ll deliver backend features in Golang for customer-facing and internal platforms, ensuring reliability and security.

You will collaborate with product, engineering, operations, and external partners, employing AI-assisted development methods and driving AI-powered workflows that retrieve data and

Qualifications

• Production-grade backend experience in a fast-moving environment.
• Hands-on experience with Golang.
• Experience designing secure and scalable software solutions.
• Strong knowledge of REST APIs, microservices, and distributed systems.
• Experience with payments, fintech, or complex integrations.
• Experience building AI-powered or agentic workflows.
• Familiarity with LLM APIs and tool calling.
• Practical testing, observability, debugging, and performance optimization.
• Excellent problem-solving and communication; fluent English.

Responsibilities

• Design, build, and operate secure, scalable payment services.
• Deliver backend features using Golang across platforms.
• Build integrations with POS systems, payment providers, and partners.
• Use AI-assisted development tools across the SDLC with quality standards.
• Design and develop AI-powered workflows that retrieve data and call tools.
• Implement permissions, guardrails, and fallback for agentic systems.
• Identify performance bottlenecks and improve speed, security, cost efficiency.
• Write clean, tested, well-documented code following security best practices.
• Contribute to technical design discussions and engineering standards.

Skills

Golang

REST APIs

Microservices

Distributed systems

Database design

AI integrations

LLM APIs

Tool calling

Retrieval-augmented generation

Observability

Testing

Performance optimization

Security

English communication

Tools

POS systems

Payment providers

CI/CD

Kubernetes

Job description

Why Qlub:

The end of a great meal shouldn't be the slow part. Waiting for the check, finding someone to take payment, splitting a bill by hand. qlub removes that friction. Guests scan a QR code and pay in seconds. No app, no download, no waiting.

From Pay-at-Table and Digital Menus to Order-and-Pay, Payment Links, and SoftPOS terminals, we handle the full payment experience so restaurants can focus on what they do best: great hospitality. Less friction means faster table turnover, smoother operations, and higher profit.

We're a fast-scaling fintech backed by Mastercard, Mubadala, e& and Shorooq. $72M raised, live across multiple markets worldwide, and headcount doubled in the past year. We're building the teams that take us to the next stage.

The role:

qlub is scaling fast across markets worldwide, and we look for people who take real ownership of their work. As our next Senior Backend Engineer – Payments, you'll help drive our growth across our engineering and payment platforms by building secure, scalable, and reliable products from day one.

You'll work closely with product, engineering, operations, and external partners to deliver seamless payment experiences for restaurants and diners. You will also use AI-assisted development practices throughout the software development lifecycle and contribute to
AI-powered and agentic systems that can reason, retrieve information, use tools, and execute controlled workflows.

If you thrive in a fast-moving, build-from-scratch environment and enjoy solving complex problems across payments, integrations, and AI-enabled software, this role is for you.

What you’ll own:

• Design, build, and operate secure, scalable, and highly reliable payment services, including payment gateways, transaction processing, reconciliation, and settlement flows
• Deliver backend features using Golang across customer-facing, restaurant-facing, and internal platforms
• Build and maintain integrations with POS systems, payment providers, financial partners, and other third-party platforms
• Use AI-assisted development tools for discovery, implementation, debugging, testing, code review, documentation, and refactoring while maintaining strong engineering quality standards
• Design and develop AI-powered and agentic workflows that can retrieve data, call tools, interact with internal systems, and execute controlled actions
• Implement appropriate permissions, human approvals, guardrails, observability, auditability, and fallback mechanisms for agentic systems
• Identify performance bottlenecks and improve the speed, reliability, security, and cost efficiency of payment and AI-powered workflows
• Write clean, maintainable, tested, and well-documented code that follows software engineering and financial-system security best practices with AI
• Contribute to technical design discussions, architecture decisions, engineering standards, and continuous improvement across the team

Who you are:

• You've built and operated production software in a fast-moving, high-growth environment
• You move fast and make strong technical decisions with incomplete information
• You take real ownership and think like an operator, not a coordinator
• You're energized by hard problems in payments, integrations, distributed systems, AI, and customer experience
• You use AI development tools pragmatically to improve speed and quality without compromising security, maintainability, or engineering judgement
• You collaborate effectively with engineers, product teams, operations teams, and external technical partners

What you’ll need:

• Proven experience building production-grade backend software applications
• Hands-on experience with Golang
• Experience designing and implementing secure and scalable software solutions
• Strong knowledge of REST APIs, microservices, asynchronous processing, and distributed systems
• Proficiency in databases, data modelling, and database design concepts
• Experience with POS systems, payment providers, or complex third-party integrations
• Experience building or integrating production AI applications
• Practical experience with LLM APIs, tool calling, retrieval-augmented generation, or agentic workflows
• Understanding of AI-system risks, including hallucinations, prompt injection, data leakage, non-deterministic behaviour, and unsafe tool execution
• Experience with automated testing, observability, debugging, and performance optimization
• Excellent problem-solving and communication skills
• Fluency in English is a must

Nice to have:

• Experience in payments, fintech, hospitality tech, or a high-growth marketplace
• Experience with payment gateways, transaction processing, settlement, reconciliation, or chargeback systems
• Experience building AI agents that interact with APIs, databases, internal tools, or operational workflows
• Experience with model evaluation, prompt management, AI observability, guardrails, or LLM cost optimization
• Experience with vector databases, embeddings, semantic search, or retrieval systems
• Experience with cloud platforms, containerized services, CI/CD, and infrastructure-as-code
• Familiarity with PCI DSS, data privacy, and secure software-development practices

What we offer:

• Real ownership over products that impact millions of diners and thousands of restaurants globally
• The opportunity to solve challenging problems in payments, hospitality, AI, and customer experience
• A fast-moving environment where great ideas quickly become reality
• Close collaboration with experienced operators, builders, and industry experts
• The opportunity to shape how AI-assisted and agentic development is used across real-world payment products
• A chance to leave a visible mark on one of the fastest-growing restaurant technology companies globally
• Ready to build? Join us and help shape how the world pays at the table.