Fullstack Engineer

Seargin Ltd; Polska; Hybrid; PLN 180,000 - 240,000; Full time

Benefits offered by this job

MultiSport

Private Medical Care

Job summary

Seargin Ltd is hiring a Senior Fullstack Engineer to design, build, and maintain a B2B portal using React, TypeScript, and modern frontend technologies. You will develop backend services with Node.js and Fastify, expose REST and GraphQL APIs, and model PostgreSQL data for catalogs, pricing, and orders.

You will optimize performance with Redis, implement server-state management with TanStack Query, and ensure strong type safety with Zod.

Qualifications

• Commercial experience as a Fullstack Engineer or frontend-focused developer delivering complex web apps.
• Strong hands-on experience with TypeScript across frontend and backend.
• Advanced React knowledge including modern routing, state management, and architecture.
• Practical experience with TanStack Query for server-state management and caching.
• Experience with Zod or similar schema validation libraries for type safety.
• Hands-on backend development with Node.js and Fastify for scalable APIs.
• Experience designing GraphQL schemas and APIs.
• Solid PostgreSQL data modeling, query optimization, and Redis caching.
• Proven B2B portal or e-commerce platform experience with ordering and account mgmt.
• Ability to own features end-to-end and communicate in English at C1 level.
• Fluent Polish and English preferred for collaboration.

Responsibilities

• Design, build, and maintain B2B portal UIs with React and TypeScript.
• Develop and maintain backend services using Node.js, Fastify, REST, and GraphQL.
• Model and optimize PostgreSQL data to support catalogs, pricing, orders, and accounts.
• Implement caching and performance improvements with Redis and related techniques.
• Fetch data with TanStack Query and enforce type-safe validation across layers.
• Create B2B e-commerce features like account hierarchies, bulk ordering, and order history.
• Integrate platform with ERP, product info services, and master data repositories via APIs.
• Collaborate with stakeholders to clarify requirements and drive feature implementation.
• Maintain code quality via testing, reviews, and engineering standards; ensure security/compliance.

Skills

TypeScript

React

TanStack Query

Schema Validation

Node.js

Fastify

GraphQL

PostgreSQL

Redis

B2B E-Commerce

English Communication

Tools

PostgreSQL

Zod

Redis

TanStack Query

REST APIs

GraphQL

Job description

• Design, build, and maintain B2B portal user interfaces using React, TypeScript, and modern frontend technologies to deliver scalable user experiences.
• Develop and maintain backend services using Node.js, Fastify, REST APIs, and GraphQL to support business-critical portal functionality.
• Data Modeling & Database Design
  • Design and optimize PostgreSQL data models supporting product catalogs, customer pricing, orders, accounts, permissions, and commerce workflows.
• Performance Optimization
  • Implement caching, session management, and application performance improvements using Redis and other optimization techniques.
• Data Fetching & Validation
  • Utilize TanStack Query for frontend data management and implement type-safe validation and contracts using Zod across application layers.
• B2B E-Commerce Features
  • Develop features including customer account hierarchies, role-based access, bulk ordering, order history, tracking capabilities, and document management.
• Integrate the platform with ERP systems, product information services, customer master data repositories, and other business applications through APIs.
• Requirements Analysis
  • Work directly with business stakeholders to clarify requirements, translate business needs into technical solutions, and drive feature implementation.
• Code Quality & Engineering Standards
  • Write clean, tested, and well-documented code while participating in code reviews and promoting development best practices.
• Security & Compliance
  • Ensure solutions meet security, privacy, compliance, and regulatory requirements expected within highly regulated business environments.

Requirements

• Fullstack Development Experience
  • Commercial experience as a Fullstack Engineer or frontend-focused developer delivering complex web applications and business-critical digital solutions.
• TypeScript Expertise
  • Strong hands-on experience with TypeScript across both frontend and backend development environments.
• React Development
  • Advanced knowledge of React, including modern routing patterns, state management, and application architecture best practices.
• TanStack Query
  • Practical experience implementing server-state management, asynchronous data fetching, and caching using TanStack Query.
• Schema Validation
  • Experience using Zod or comparable schema validation libraries to ensure type safety and consistent data handling.
• Node.js & Fastify
  • Hands-on backend development experience using Node.js and Fastify for scalable API and service development.
• GraphQL Development
  • Experience designing GraphQL schemas, developing APIs, and implementing efficient data access strategies.
• Strong knowledge of PostgreSQL data modeling, query optimization, performance tuning, and Redis-based caching or session management.
• B2B E-Commerce Platforms
  • Proven experience building B2B portals or e-commerce solutions involving ordering, pricing, user management, and account administration processes.
• Ownership & Communication Skills
  • Ability to independently own features end-to-end, make sound technical decisions, and communicate effectively in English at C1 level.
• Language Skills
  • Fluent Polish and English language skills supporting collaboration with stakeholders and project teams.

What we offer

• B2B Contract
  • Employment based on a B2B contract
• Stable and Dynamic International Firm
  • Opportunity to work in a stable, dynamically developing international company
• Engaging Projects and Latest IT
  • Chance to participate in interesting projects and work with the latest information technologies
• Competitive Rates
  • Attractive remuneration rates offeres
• Renowned International Projects
  • Involvement in the most prestigious international project
• MultiSport and Private Medical Care
  • MultiSport and Private Medical Care

Nice to have

• Headless Commerce Platforms
  • Experience with modern commerce platforms and composable commerce architectures used in B2B environments.
• ERP Integrations
  • Experience integrating web applications with SAP or other ERP platforms through APIs and enterprise integration patterns.
• Pharma Industry Knowledge
  • Understanding of pharmacy distribution, healthcare commerce processes, and regulated product management requirements.
• Compliance & Data Privacy
  • Knowledge of GxP, GDPR, and compliance requirements relevant to regulated industries.
• Experience with Azure or AWS, containerization technologies, and CI/CD implementation practices.
• Automated Testing
  • Hands-on experience with automated testing frameworks for unit, integration, and end-to-end testing.
• Experience working with monorepo architectures and tools supporting large-scale application development.
• Accessibility & Performance
  • Knowledge of WCAG accessibility standards and frontend performance optimization techniques.
• Previous experience delivering solutions for large enterprise organizations operating in regulated industries.

Work with us