Fullstack Engineer

Seargin; Polska; Remote; PLN 200,000 - 360,000; Full time

Job summary

Seargin seeks a Principal Engineer for a remote, B2B e-commerce portal project in pharma/health. You will own features end-to-end, from data model and API through to the user interface, in a multinational environment.

You will lead complex UI and backend work, uphold security and data privacy in regulated contexts, and drive architecture decisions. The role demands strong TS across FE/BE, advanced React expertise, GraphQL, PostgreSQL modelling, and experience with ERP integrations.

Qualifications

• Commercial experience as a full-stack or frontend-heavy developer.
• Strong, hands-on TypeScript across frontend and backend.
• Advanced React experience, including React Router 7.
• Practical experience with TanStack Query (React Query).
• Experience with Zod or similar schema validation library.
• Backend development in Node.js with Fastify.
• GraphQL – designing schemas and APIs.
• PostgreSQL – data modelling and performance tuning.

Responsibilities

• Design, build and maintain the B2B portal front end in React with TypeScript.
• Build and maintain backend services in Fastify with REST and GraphQL.
• Model PostgreSQL data for product catalog, pricing, orders and accounts.
• Implement Redis caching and session handling, optimize performance.
• Manage client state with TanStack Query for frontend data.
• Enforce type-safe contracts using Zod between front end and back end.
• Develop features like account hierarchies, roles, and bulk ordering.
• Integrate the portal with ERP and product data via APIs.
• Write clean, tested, documented code and participate in reviews.
• Ensure security, privacy, and compliance in pharma/health context.

Skills

Full-stack experience

TypeScript

React expertise

React Router 7

TanStack Query

Zod schema validation

Node.js (Fastify)

GraphQL APIs

PostgreSQL modelling

Redis caching

English (C1)

B2B portal experience

Tools

React

TypeScript

Fastify

Node.js

GraphQL

PostgreSQL

Redis

TanStack Query

Zod

Job description

As a dynamic multinational tech company operating in 50 countries, we drive innovation and create projects that shape the future and greatly enhance the quality of life. You will find our solutions in the space industry, supporting scientists in the development of cancer drugs, and implementing innovative technological solutions for industrial clients worldwide. These are just some of the areas in which we operate!

Currently, for the new Seargin project we are looking for a Principal Engineer.

Location: Remote

Employment Type: b2b contract

FTE: full-time

The company’s initiative to build a B2B e-commerce portal for its pharmacy channel. The portal will let pharmacies and pharmacy chains browse products, place and track orders, and manage their accounts with company. The consultant will join as a senior full-stack developer able to own features end to end, from data model and API through to the user interface.

Key Tasks and Responsibilities

• Design, build and maintain the B2B portal front end in React with TypeScript, using React Router 7 for routing and data loading.
• Build and maintain backend services in Fastify (Node.js / TypeScript), including REST and GraphQL APIs.
• Design and optimise the PostgreSQL data model for B2B commerce domains such as product catalogue, customer-specific pricing, orders, accounts and user roles.
• Implement caching, session handling and performance optimisation with Redis.
• Manage server state and data fetching on the front end with TanStack Query.
• Implement schema validation and type-safe contracts across front end and back end using Zod.
• Build typical B2B portal features: customer account hierarchies, role-based access, bulk and repeat ordering, order history and tracking, invoices and document access.
• Integrate the portal with company’s internal systems (e.g. ERP, product information, customer master data) via APIs.
• Work independently with business stakeholders to clarify requirements and translate them into technical solutions.Write clean, tested, documented code and take part in code reviews.
• Ensure the solution meets security, data privacy and compliance standards expected in a regulated pharma/consumer health environment.

What we’re looking for:

• Commercial experience as a full-stack or front-end-heavy developer.
• Strong, hands-on TypeScript across front end and back end.
• Advanced React experience, including React Router (ideally v7 / Remix-style data loading).
• Practical experience with TanStack Query (React Query).
• Experience with Zod or a comparable schema validation library.
• Backend development in Node.js with Fastify.
• GraphQL - designing schemas and building APIs.
• PostgreSQL - data modelling, query writing and performance tuning.
• Redis - caching and/or session management.
• Proven experience building B2B portals or B2B e-commerce platforms (ordering, pricing, account management).
• Experience working in or for pharmaceutical, healthcare or consumer health companies.
• Ability to work independently, take ownership of features and make sound technical decisions with minimal supervision.
• English at C1 level, spoken and written, for daily communication with international stakeholders.

Nice to have:

• Polish language (native or fluent).
• Experience with headless commerce platforms (e.g. commercetools, Shopify Plus B2B, SAP Commerce / Hybris, Salesforce B2B Commerce).
• Integration experience with SAP or other ERP systems.
• Knowledge of the pharmacy / pharma distribution channel and its specifics (wholesalers, pharmacy chains, regulated product handling).
• Familiarity with GxP or other pharma compliance and data privacy requirements (GDPR).
• Cloud experience (Azure or AWS), Docker and CI/CD pipelines.
• Automated testing experience (Vitest/Jest, Playwright or Cypress).
• Experience with monorepo tooling (Nx, Turborepo).
• Accessibility (WCAG) and front-end performance optimisation.
• Previous work with large FMCG/pharma clients.

Contact: [e-mail]

To learn more about Seargin, please visit our web page: www.seargin.com