Senior Full-Stack Developer – Mobile Backend Refactoring (Node.js / Flutter)

Filled
February 26, 2026
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Job Description

Project Type: Contract / Long-term
Location: Remote

About the Role

We are looking for a Senior Full-Stack Developer to help refactor and modernize the backend of our language learning app. The current setup is monolithic and has accumulated technical debt. You will be responsible for moving the platform to a scalable, service-oriented architecture, improving performance, and ensuring maintainable, high-quality code.

Key Responsibilities

  • Upgrade backend stack: Node.js 17 → Node.js 20 LTS, Sequelize v5 → v6+
  • Refactor logic from Controllers → Services/Repositories for cleaner architecture
  • Optimize CPU-heavy “Challenge Progress” logic using persistent DB/cache state
  • Audit and consolidate PostgreSQL & MongoDB to reduce latency and improve queries
  • Decouple local app content into a Dynamic API
  • Implement Winston/Sentry logging and maintain Swagger documentation
  • Enforce strict Flutter linting & analysis using analysis_options.yaml

Requirements

  • Expert in Node.js, Clean Architecture, and backend performance optimization
  • Proven experience handling breaking changes in ORM migrations
  • Strong ability to eliminate technical debt, standardize error handling, and implement maintainable services
  • Experience with Flutter code quality enforcement
  • Familiarity with PostgreSQL & MongoDB in high-performance environments

Preferred Skills

  • Experience migrating monolithic apps to service-oriented architectures
  • Knowledge of caching strategies for high-load applications
  • Proficiency with logging, monitoring, and error tracking