Fullstack Developer - Merchant Application (70% Front End)

Our client, Canada's largest retailer,is seeking a Senior Fullstack Developer to own end-to-end proprietary merchant application features using Next.js, React, TypeScript, Kotlin, and Spring Boot

Start Date: ASAP

End Date: December 2026, with extension to 2027

Location: Hybrid (3 days onsite) - Brampton and/or Downtown Toronto

Full Stack Developer (Frontend-Focused)

We are seeking a Frontend-focused Full Stack Developer to own the design, development, testing, and delivery of features for a new high-visibility project involving the development of a brand new merchant service platform. This role is approximately 70% frontend and 30% backend , with a strong emphasis on building modern React applications while contributing to backend services when needed.

The ideal candidate has strong experience with React and Next.js , understands up-to-date frontend architecture and component design, and is comfortable working with REST APIs and Java-based backend services. While Kotlin, GCP, and several supporting libraries are used within our setting, they are considered nice-to-have skills and can be learned on the job.

Top Required Skills:

- Strong experience building applications with React (Next.js experience preferred)
- Experience with Java (Kotlin is a plus but not required)
- Experience building reusable frontend components using Atomic Design principles
- Experience designing and consuming REST APIs
- Strong unit testing experience using Jest (frontend) and/or JUnit (backend)

Key Responsibilities:

- Design and develop responsive, reusable user interfaces using React , Next.js (App Router) , TypeScript , and Tailwind CSS .
- Build scalable frontend applications using modern React patterns and shared component libraries.
- Create reusable UI components following Atomic Design principles.
- Develop data-driven interfaces that integrate with backend REST APIs.
- Implement client-side state management and asynchronous data fetching using modern React libraries.
- Build forms with validation and provide accessible, user-friendly experiences.
- Contribute to backend services using Java/Spring Boot or Kotlin/Spring Boot , developing and maintaining REST APIs.
- Participate in end-to-end feature development across the frontend, backend, and data layers.
- Write comprehensive unit and integration tests to ensure application quality and maintainability.
- Collaborate with product managers, designers, and engineers to deliver high-quality features.
- Participate in code reviews and promote engineering best practices.

Required Qualifications:

- Experience with Next.js is preferred.
- Experience developing backend services with Java and Spring Boot (Kotlin experience is an asset but not required).
- Solid understanding of RESTful API development and integration.
- Experience writing automated unit tests using Jest and/or JUnit .
- Experience building reusable component libraries using Atomic Design or similar component-driven architecture.
- Strong understanding of Git workflows and collaborative software development.

Nice-To-Have Qualifications:

Experience with any of the following is considered an asset:

- Kotlin
- Google Cloud Platform (Firestore, BigQuery, GKE, GCS)
- AWS or Azure cloud platforms
- TanStack React Query
- TanStack React Table
- next-intl
- React Hook Form and Zod
- Spring Security
- Firebase Remote Config
- Docker, Helm, and GitLab CI/CDSentry, Micrometer,



and application monitoring tools

Technical Environment:

Frontend:

- React
- Next.js
- TypeScript
- Tailwind CSS
- React Query
- React Hook Form
- Jest
- React Testing Library
- Spring Boot
- REST APIs
- Spring Security
- JUnit

Libraries, Services & Infrastructure:

- Feature flags: Firebase Remote Config
- Cloud platform: GCP (Secret Manager, GCS, GKE)
- Monitoring: Sentry (UI), Micrometer / Stackdriver (backend)
- Firestore
- BigQuery
- Docker

Domain & Soft Skills:

- Retail / merchandising workflow concepts (human-in-the-loop approvals)
- Multi-tenant or scoped data access patterns
- Strong testing discipline and code quality practices
- Comfort with feature flags and gradual rollout

What We're Looking For:

- We're looking for an engineer who enjoys building intuitive user experiences and is comfortable owning features from concept to deployment. The strongest candidates will have deep React expertise, solid Java backend experience, excellent testing practices, and a collaborative approach to software development. Experience with Kotlin, GCP, and our supporting frontend libraries is beneficial but can be learned by a strong developer with the right fundamentals.

Fullstack Developer - Merchant Application (70% Front End)

Our client, Canada's largest retailer,is seeking a Senior Fullstack Developer to own end-to-end proprietary merchant application features using Next.js, React, TypeScript, Kotlin, and Spring Boot

Start Date: ASAP

End Date: December 2026, with extension to 2027

Location: Hybrid (3 days onsite) - Brampton and/or Downtown Toronto

Full Stack Developer (Frontend-Focused)

We are seeking a Frontend-focused Full Stack Developer to own the design, development, testing, and delivery of features for a new high-visibility project involving the development of a brand new merchant service platform. This role is approximately 70% frontend and 30% backend , with a strong emphasis on building modern React applications while contributing to backend services when needed.

The ideal candidate has strong experience with React and Next.js , understands modern frontend architecture and component design, and is comfortable working with REST APIs and Java-based backend services. While Kotlin, GCP, and several supporting libraries are used within our environment, they are considered nice-to-have skills and can be learned on the job.

Top Required Skills:

- Strong experience building applications with React (Next.js experience preferred)
- Experience with Java (Kotlin is a plus but not required)
- Experience building reusable frontend components using Atomic Design principles
- Experience designing and consuming REST APIs
- Strong unit testing experience using Jest (frontend) and/or JUnit (backend)

Key Responsibilities:

- Design and develop responsive, reusable user interfaces using React , Next.js (App Router) , TypeScript , and Tailwind CSS .
- Build scalable frontend applications using modern React patterns and shared component libraries.
- Create reusable UI components following Atomic Design principles.




- Develop data-driven interfaces that integrate with backend REST APIs.
- Implement client-side state management and asynchronous data fetching using modern React libraries.
- Build forms with validation and provide accessible, user-friendly experiences.
- Contribute to backend services using Java/Spring Boot or Kotlin/Spring Boot , developing and maintaining REST APIs.
- Participate in end-to-end feature development across the frontend, backend, and data layers.
- Write comprehensive unit and integration tests to ensure application quality and maintainability.
- Collaborate with product managers, designers, and engineers to deliver high-quality features.
- Participate in code reviews and promote engineering best practices.

Required Qualifications:

- Strong professional experience with React and modern JavaScript/TypeScript.
- Experience with Next.js is preferred.
- Experience developing backend services with Java and Spring Boot (Kotlin experience is an asset but not required).
- Solid understanding of RESTful API development and integration.
- Experience writing automated unit tests using Jest and/or JUnit .
- Experience building reusable component libraries using Atomic Design or similar component-driven architecture.
- Strong understanding of Git workflows and collaborative software development.

Nice-To-Have Qualifications:

Experience with any of the following is considered an asset:

- Kotlin
- Google Cloud Platform (Firestore, BigQuery, GKE, GCS)
- AWS or Azure cloud platforms
- TanStack React Query
- TanStack React Table
- Zustand
- next-intl
- React Hook Form and Zod
- Spring Security
- Microsoft Entra ID (Azure AD)
- Firebase Remote Config
- Docker, Helm, and GitLab CI/CD
- Sentry, Micrometer, and application monitoring tools

Technical Environment:

Frontend:

- React
- Next.js
- TypeScript
- Tailwind CSS
- React Query
- React Hook Form
- Jest
- React Testing Library

Backend:

- Java / Kotlin
- Spring Boot
- REST APIs
- Spring Security
- JUnit

Libraries, Services & Infrastructure:

- Database : Google Cloud Firestore
- Analytics / data pipeline: Google BigQuery
- Authentication: Microsoft Entra ID (Azure AD) JWT
- Feature flags: Firebase Remote Config
- Cloud platform: GCP (Secret Manager, GCS, GKE)
- Monitoring: Sentry (UI), Micrometer / Stackdriver (backend)
- CI/CD: GitLab CI, Docker (Jib), Helm

Cloud & Infrastructure:

- Google Cloud Platform (preferred)
- Firestore
- BigQuery
- Docker
- Helm
- GitLab CI/CD

Domain & Soft Skills:

- Retail / merchandising workflow concepts (human-in-the-loop approvals)
- Multi-tenant or scoped data access patterns
- End-to-end feature ownership (UI -> API -> data layer)
- Cross-repo development (frontend, backend, shared packages)
- Strong testing discipline and code quality practices
- Comfort with feature flags and gradual rollout

What We're Looking For:

- We're looking for an engineer who enjoys building intuitive user experiences and is comfortable owning features from concept to deployment. The strongest candidates will have deep React expertise, solid Java backend experience, excellent testing practices, and a collaborative approach to software development. Experience with Kotlin, GCP, and our supporting frontend libraries is beneficial but can be learned by a strong developer with the right fundamentals.

Disclaimer:
AI may be used in evaluating candidates.
This posting is for an existing vacancy.

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📌 Fullstack Developer - Merchant Application (70% Front End) (Toronto)
🏢 S.i. Systems
📍 Toronto