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Senior Fullstack Developer (NestJS/ React.js)

1 month, 2 weeks ago
Poland, Ukraine
Full-time
Senior
Full-stack Engineer
Software Development
Agile AWS Confluence Docker EC2 Elasticsearch GitHub Actions Jest JIRA JWT Microservices NestJS Node.js PostgreSQL Prisma React Redis REST API Scrum Supertest TDD Terraform TypeScript
Apply Now
Symphony Solutions

Symphony Solutions

Symphony Solutions is a Cloud and Agile transformation company headquartered in the Netherlands, with delivery centers in Ukraine, Poland, Macedonia, and The Netherlands. Founded in 2008, the company is now 600 people with over 35 international clients...

Internet Software & Services
251-1K
Founded 2008
View All Jobs 10

Description

  • Build and harden the NestJS backend, including persistent user accounts, JWT-based authentication, role-based access, and full tenant isolation across API endpoints.
  • Migrate financial calculations to BigInt arithmetic in minor currency units to ensure Gross Gaming Revenue calculations are accurate to the cent.
  • Implement an immutable AuditLog across onboarding, settlement, configuration, and user-management flows so every data mutation is captured and exportable.
  • Design and deliver management APIs for Operator CRUD, Provider creation, and User Management with strict validation and role-based permissions.
  • Improve performance through database indexing, Redis caching strategies, and elimination of N+1 query issues.
  • Build the provider-facing React 19 frontend, including the login experience, auth flow, modular app structure, operator onboarding screens, and live revenue dashboards.
  • Write unit and integration tests and collaborate with QA on E2E, load, and UAT cycles.
  • Use AI-assisted development tools to support coding, testing, debugging, refactoring, and documentation tasks.
  • Resolve technical issues and bug-fix implemented features as they arise.
  • Communicate with the Product team and engineering colleagues, participate in Scrum ceremonies, and mentor junior team members as needed.

Requirements

  • 5+ years of total software development experience.
  • 3+ years of production experience with React, including complex state management using Redux, Redux Toolkit, React Query, Zustand, or similar tools.
  • 3+ years of Node.js and TypeScript backend experience, ideally with NestJS in a production API or BFF layer.
  • Strong proficiency in TypeScript across both frontend and backend.
  • Hands-on experience with Prisma ORM or a comparable ORM and PostgreSQL, including performant queries and index design.
  • Solid understanding of authentication and authorization patterns, including JWT access and refresh tokens, RBAC/Guards, session security, and multi-tenant data isolation.
  • Experience designing and consuming REST APIs in a microservices or BFF architecture, including request validation, error handling, and contract stability.
  • Working knowledge of AWS services such as EC2, RDS, ElastiCache, S3, ALB, CloudWatch, and Secrets Manager, plus CI/CD with GitHub Actions.
  • Familiarity with Docker and Docker Compose, along with basic containerized deployment workflows.
  • Experience with unit and integration testing using Jest, Vitest, Supertest, or similar tools.
  • Strong English communication skills at B2+ level.
  • Self-organized, proactive, and comfortable working in a distributed team.
  • Daily use of AI-assisted development tools such as Claude, Cursor, GitHub Copilot, and ChatGPT for code generation, refactoring, debugging, testing, and documentation.
  • Ability to apply AI tools to real SDLC tasks such as scaffolding NestJS modules and React components, generating and reviewing tests, debugging production-grade TypeScript, drafting technical documentation, and reasoning about migrations.
  • Awareness of AI limitations in a regulated, financial-grade context, with every AI-assisted change reviewed, tested, and traceable through code review and an immutable audit log.
  • Experience working in regulated industries such as iGaming under UKGC or MGA, financial services, or healthcare, with awareness of GDPR, audit logging, and PII handling.
  • Experience with financial-grade calculations, including BigInt arithmetic in minor currency units, FX handling, and reconciliation logic.
  • Experience implementing immutable audit logs, HMAC event signing, or other tamper-evident data flows.
  • Familiarity with Redis caching patterns, query performance tuning, and N+1 query elimination.
  • Hands-on experience with Terraform or other Infrastructure-as-Code tooling.
  • Experience with Elasticsearch or comparable search and analytics engines.
  • Experience with TDD and code-review-driven development.
  • Experience with JIRA and Confluence in an Agile/Scrum environment.
  • Background in iGaming or online gaming platforms.

Interested in this position?

Apply directly on the company website

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