Senior Software Engineer in Vaughan

We are seeking a highly skilled Senior Full-Stack Developer with 6+ years of experience to lead the digital transformation of our core enterprise applications. You will be responsible for the end-to-end modernization of legacy .NET Framework 4.8 MVC monoliths into high-performance, .NET 6+ and up microservices and APIs, paired with a modern React frontend and hosted on AWS. This is not a 'maintenance' role; it is a 're-engineering' role. You will bridge the gap between reliable legacy logic and the future-proof scalability of modern cloud architecture.

Key Responsibilities

• Legacy Deconstruction: Analyze existing .NET 4.8 MVC applications to identify business logic, dependencies, and integration points for migration.
• Architecture Migration: Lead the transition from monolithic architectures to modern design patterns (Microservices, Hexagonal, or Clean Architecture).
• Backend Modernization: Rewrite and refactor legacy C# code to .NET 6/8+, implementing cross-platform compatibility and improved performance.
• Frontend Revolution: Replace Razor/Server-side rendering with a decoupled, state-of-the-art React SPA (Single Page Application) using TypeScript and modern state management (Redux Toolkit, TanStack Query).
• Cloud Orchestration: Design and deploy the modernized stack on AWS, leveraging services like Lambda, ECS (Fargate), S3, and RDS.
• API Design: Build robust, secure RESTful APIs that serve as the bridge between the new React frontend and the modernized backend.
• CI/CD Implementation: Establish automated pipelines for building, testing, and deploying both the .NET and React components.

Technical Requirements

• Backend Expertise
• Legacy: Deep understanding of .NET Framework 4.8, ASP.NET MVC, and Web API.
• Modern: Expert-level proficiency in .NET 6/7/8 and ASP.NET Core.
• Language: Advanced C# skills (Generics, LINQ, Async/Await, Dependency Injection).
• Database: Experience with SQL Server (T-SQL) and migrating to AWS-managed databases (RDS/Aurora).
• Frontend Expertise
• React: Strong experience with Functional Components, Hooks, and modern React patterns.
• Languages: JavaScript (ES6+) and TypeScript (Required).
• Tools: Experience with Vite or Webpack, and CSS frameworks (Tailwind, Material UI).
• Cloud & DevOps (AWS)
• Compute: Hands-on experience with AWS Lambda (Serverless) or Amazon ECS/EKS.
• Infrastructure: Familiarity with Infrastructure as Code (CloudFormation, CDK, or Terraform).
• Deployment: Building CI/CD pipelines (GitHub Actions).

Preferred Qualifications

• Experience using the AWS Porting Assistant for .NET or AWS Transform.
• Familiarity with containerization (Docker) and orchestration.
• Knowledge of Authentication/Authorization standards (OAuth2, OpenID Connect, AWS Cognito).
• Proven track record of successfully migrating at least one large-scale enterprise application.

GFL is committed to equal opportunity for all, without regard to race, religion, color, national origin, citizenship, sex, sexual orientation, gender identity, age, veteran status, disability, genetic information, or any other protected characteristic. Please note that GFL does not provide visa sponsorship for this position. Valid work authorization in the country where the job is located is required. Successful candidates will be required to provide valid documentation confirming their eligibility to work in the country where the job is located prior to their start date. This hiring process may utilize machine-based systems to assist in screening and assessing applicants. Final selection decisions are made by our recruitment team.

At GFL, growth isn’t just for our business—it’s for our people. Because we see the potential in all our employees to do whatever it is they set their mind to, and we’re proud to support them in that journey. We consider our employees’ personal goals, helping them create the career, and life, that they desire—whether it’s advancing in their job, learning new skills, forming lasting relationships, or mentoring others, while having time to pursue other life ambitions. With safety and sustainability at the core of what we do, we all come together to form “Team Green”—united by our shared purpose to provide environmental solutions that enable our customers and the communities we serve to be Green For Life.