Sr. Full Stack Developer [.NET and JavaScript (React JS, JSON, and Node.js)] to support building, maintaining, and scaling web applications
S.i. Systems
Toronto, ON-
Number of positions available : 1
- Salary To be discussed
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Contract job
- Published on September 10th, 2025
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Starting date : 1 position to fill as soon as possible
Description
Our valued client is looking for a Sr. Full Stack Developer [.NET and JavaScript (React JS, JSON, and Node.js)] to support building, maintaining, and scaling web applications
A 1 year contract. 100% remote. Must work EST time zone. 7.5 hour work days.
Tasks include:
- Build, maintain, and scale modern web applications that serve both internal and external clients
- This role bridges front-end and back-end development, requiring a deep understanding of architecture, performance optimization, and user experience
- Design, develop, and maintain responsive web applications using React.js and .NET Core.
- Build and maintain robust RESTful APIs and microservices with Node.js and .NET.
- Integrate and parse structured data using JSON for communication between front-end and back-end systems.
- Collaborate with UI/UX designers, PO, BA, DevOps engineers, and QA to deliver high-quality products.
- Troubleshoot, debug, and upgrade software and perform regular code reviews.
- Work within an Agile/Scrum environment to meet sprint deadlines and deliverables.
- Ensure application performance, scalability, and security
- Develop a full-featured customer-facing platform with real-time data updates and analytics
- Implement single-page applications (SPAs) using React that consume backend APIs
- Design back-end services in .NET Core and Node.js, optimized for performance and scalability
- Handle large volumes of data exchange using JSON with strong error handling and validation
- Participate in containerization and cloud deployment (AWS or Azure) as part of CI/CD pipeline
Must have Skills:
- Reliability security clearance
- Experience as a Full Stack Developer building Front-end applications
- Proven experience in building robust and scalable front-end applications using modern JavaScript (ES6+). Strong understanding of core JavaScript concepts, asynchronous programming, and browser-based development best practices
- Hands-on experience designing and implementing RESTful APIs. Skilled in creating clean, maintainable endpoints that support efficient data exchange between front-end and back-end systems, with a focus on performance, security, and scalability
- React.js and JavaScript - Advanced front-end development skills for building modern UI components and managing state
- .NET Core - Solid experience in building scalable and maintainable APIs and services
- Node.js + JSON - Proficiency in building middleware and working with structured data interchange formats
- Demonstrates familiarity with application security tools such as Software Composition Analysis (SCA) and Static Application Security Testing (SAST)
- Capable of identifying and monitoring application insights to effectively debug and resolve issues
- Leads technical discussions and conducts peer code reviews to uphold high-quality coding standards
Nice to have:
- Bachelor’s degree in computer science or equivalent experience
- Experience with TypeScript, Redux, or GraphQL.
- Exposure to Docker, Kubernetes, and cloud platforms like Azure or AWS.
- Familiarity with CI/CD pipelines and test automation tools (Jest, Mocha, xUnit).
- Knowledge of database systems like SQL Server, MongoDB, or PostgreSQL
Requirements
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