Senior Fullstack (Node.js + React.js)

OnHires; Warszawa; Hybrid; PLN 338,000 - 423,000; Full time

Job summary

A product-based SaaS company is seeking a Senior SDE Fullstack to take ownership of backend and frontend feature development in a hybrid environment in Warsaw. The role demands strong expertise in Node.js, NestJS, React.js, and TypeScript, along with experience in building secure REST APIs and managing CI/CD pipelines. Competitive compensation and an annual learning budget are offered.

Benefits

Competitive compensation

22 paid vacation days + national holidays

Annual learning & development budget

Qualifications

• 5+ years of professional full‑stack engineering experience.
• Strong production experience with Node.js, NestJS, React.js, Next.js, TypeScript.
• Solid PostgreSQL knowledge (data modeling, optimization, indexing).
• Strong experience with AWS services (Lambda, S3, CloudWatch, SNS/SQS).
• Experience building secure REST APIs (JWT auth, security best practices).
• Understanding scalable architectures and basics of distributed systems.
• Docker experience.

Responsibilities

• Build and deliver complex features end‑to‑end using the outlined tech stack.
• Design and implement scalable backend services and secure REST APIs.
• Develop performant frontend components and manage state.
• Participate in architectural discussions.
• Troubleshoot and optimize backend and frontend performance.

Skills

Node.js

NestJS

React.js

Next.js

TypeScript

PostgreSQL

AWS Services

REST APIs

Docker

CI/CD Pipelines

GitHub Actions

Job description

Job Location & Details

Location: Warsaw, Poland (Hybrid — 2–3 days/week in the office)

Employment: Full-time, B2B contract

Language: English

About the Company

The hiring company is an independent product‑based SaaS organization with a portfolio of 10+ in‑house B2C digital products. The company builds and scales its own products - no outsourcing, no external clients, and no investor pressure. The engineering function operates in a hybrid model in Warsaw, where collaboration 2–3 days per week in the office is required.

About the Role

The company is seeking a Senior SDE Fullstack who will take full hands‑on ownership of backend and frontend feature development, contribute to architecture decisions, ensure performance, and maintain code quality across a modern SaaS environment.

This is a senior individual contributor role, fully hands‑on - without people‑management responsibilities.

What You’ll Do

Hands‑On Engineering (Backend & Frontend)

• Build and deliver complex features end‑to‑end using Node.js, NestJS, React.js, Next.js, TypeScript.
• Design and implement scalable backend services and secure REST APIs.
• Develop performant frontend components, SSR flows, routing, and state management.
• Write clean, maintainable, well‑tested code.
• Participate in architectural discussions within the product team.

Performance, Reliability & Observability

• Implement and refine logging, monitoring, and alerting (Sentry, Datadog, Groundcover).
• Troubleshoot and optimize backend and frontend performance.
• Participate in incident resolution and root‑cause analysis.
• Improve system reliability, traceability, and error visibility.

CI/CD, Git & DevOps Collaboration

• Maintain and enhance CI/CD pipelines (including GitHub Actions).
• Work with DevOps to ensure consistent and stable environments across dev/staging/production.
• Manage and contribute to Git branching strategies (Git Flow or Trunk‑Based Development).
• Ensure smooth, efficient, predictable deployment workflows.

Tech Stack Requirements

Must‑Have

• 5+ years of professional full‑stack engineering experience
• Strong production experience with:
  • Node.js, NestJS
  • React.js, Next.js
  • TypeScript
• Solid PostgreSQL knowledge (data modeling, optimization, indexing)
• Strong experience with AWS services (Lambda, S3, CloudWatch, SNS/SQS or equivalents)
• Experience building secure REST APIs (JWT auth, security best practices)
• Understanding scalable architectures and distributed systems basics
• Hands‑on experience with CI/CD pipelines and GitHub Actions
• Docker experience
• Experience managing Git branching strategies (Git Flow / Trunk‑Based Development)
• Ability to work hybrid in Warsaw (2–3 days/week in the office)

Nice‑to‑Have (Strong Plus)

• Kubernetes (K8s)
• ArgoCD or GitOps workflows
• Event‑driven systems (Kafka, RabbitMQ, AWS SNS/SQS)
• Infrastructure as Code (Terraform)
• Observability tooling (Sentry, Datadog, Groundcover)
• Experience with design systems / Storybook
• Experience with internal utilities or shared packages
• Experience with test automation frameworks (Playwright or similar)

Key Performance Indicators (KPIs)

• Reliable end‑to‑end feature delivery
• Architecture clarity and maintainability
• Production stability & incident resolution speed
• CI/CD stability and deployment quality
• Code quality, documentation, and testing discipline

What the Company Offers

• Competitive compensation
• 22 paid vacation days + national holidays
• Annual learning & development budget (courses, certifications, conferences)
• Opportunity to contribute to a fast‑growing multi‑product SaaS environment
• Modern technology stack with minimal legacy
• Hybrid work model with a Warsaw‑based office
• Senior, autonomous engineering culture focused on product impact

Interview Process

1. External recruiter call (30 min) – introduction, expectations
2. Recruiter Interview (prescreen, scorecard, expectations)
3. Technical Interview
4. SDE Challenge
   • 1‑day test assignment
   • Must be submitted within 5 days
5. Second Technical Interview
6. HR Interview (Professional skills, ways of working, cultural philosophy)