Senior Backend Engineer - Payments & AI-Driven Growth

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

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