Senior FullStack Developer (AI, Product, Node/React)

Location: Warsaw, Poland
Format: On-site
Seniority level: Senior

At EPC Network, we're not just a digital marketing company, we're a platform for career transformation and personal growth. Our people-first approach shapes our corporate culture, fostering a team of passionate, smart, and energetic individuals who strive to grow professionally in an international, fast-paced environment.

As a Senior FullStack Developer, you'll build and own AI-powered internal products and automation platforms end-to-end — from UI to backend services, LLM integrations, and production reliability. You will work closely with the AI team, product stakeholders, and marketing teams, and report to the Lead of AI.

Key Responsibilities:

• Design, develop, and maintain scalable front-end and back-end solutions for internal platforms, automation workflows, and third-party integrations
• Build and maintain reliable integrations with external APIs and services, including authentication, webhooks, retries, rate limits, and error handling
• Design and configure n8n workflows for automated social media publishing across LinkedIn, X, Threads, and Instagram, including UTM tracking and related automation
• Build and maintain asynchronous processing using BullMQ — queues, workers, schedulers, retries, and failure handling
• Ensure production reliability through structured logging, monitoring, metrics, alerting, and effective troubleshooting
• Write and maintain unit, integration, and end-to-end tests to ensure code quality and system stability
• Participate in code reviews, contribute to architectural decisions, and continuously improve engineering practices
• Take ownership of features end-to-end — from technical design and implementation to deployment, monitoring, and production support

Requirements:

• 4+ years of commercial software development experience, primarily in full-stack or backend-heavy roles
• 1+ year of hands-on experience building AI/LLM-powered applications or features
• Strong proficiency in JavaScript/TypeScript (Node.js) or Python (FastAPI), plus solid production experience with React
• Strong practical experience with REST APIs, webhooks, and third-party integrations
• Experience designing and maintaining asynchronous/background workflows: queues, workers, retries, idempotency, rate limiting, failure handling
• Solid knowledge of PostgreSQL and Redis — data modeling, indexing, transactions, caching, performance
• Ability to design backend services and make architectural decisions independently
• Experience with unit/integration testing, debugging, and maintaining production systems
• Practical knowledge of Docker, CI/CD, configuration and secrets management
• Understanding of web application security, authentication, and authorization
• Hands-on experience with LLM APIs, structured outputs/tool calling, and production AI integrations; understanding of RAG, embeddings/vector databases, and LLM evaluation is a plus
• Experience with n8n or similar automation tools is a plus
• Ability to work independently, investigate ambiguous technical problems, and own features from design to production
• English — Intermediate+ (B1/B2+)

What it means to be part of our Team:

• Multinational and intercultural experience
• Corporate library
• Growth opportunities, сutting-edge frameworks and technologies
• Plenty of engaging team-building and social events
• Bonuses according to the policy
• 21 paid vacation days & 14 paid sick leaves
• Cozy office in Warsaw, Kyiv available for you whenever you need it
• Coffee, tea, Red Bull, sweets, fruits, and more snacks

💌 Interested?

We're always on the lookout for passionate, driven, and curious people to join our team. If that sounds like you — we'd love to hear from you!