Senior Full Stack Engineer Jobs in Ontario (NOW HIRING)

Who We Are 

At KEV, we build mission-critical financial software for K-12 schools on a massive scale. Our platform delivers real-time control and visibility into every dollar collected, whether cash, check, or digital, replacing fragmented workflows with secure, modern systems.  

Trusted by 27,000 K-12 schools and districts managing over $8B annually, KEV operates at the intersection of payments, accounting, and reporting-where complexity is high and engineering excellence matters. Headquartered in Toronto with teams across North America, we are scaling fast and investing deeply in cloud-native, data-driven technology.  

If you want to build high-impact SaaS products that solve hard problems, scale with purpose, and make your work matter in public education, KEV is the place to do it. 

About the Role 

At KEV, our engineering teams build and operate mission-critical SaaS platforms that support more than 27,000 K12 schools and over 1 million users across North America. Our systems process and manage high volumes of financial transactions every day, operating at scale in a domain where reliability, security, and correctness are non-negotiable. 

We are hiring a Senior Developer to help design, evolve, and scale the core systems that power KEV's financial platform. In this role, you will work across frontend and backend services to deliver secure, high-performance software that supports complex financial workflows. You will contribute to architectural decisions, system design, and platform evolution as KEV continues to grow. 

This role requires deep experience building and operating SaaS software at scale. You will design systems that remain reliable under real-world load, handle sensitive financial data with care, and support distributed architectures as usage grows. You will collaborate closely with Product, Design, and Engineering peers to translate real school needs into scalable, durable solutions that earn long-term trust. 

This role is for an active vacancy. 

How You'll Contribute 

Build and Scale Core Systems 
Design, build, and evolve core services and platform capabilities that support KEV's SaaS products at scale. Lead system design and architectural decisions, including event-driven patterns where appropriate, to ensure reliable, high-performance systems across complex, high-volume workloads. 

Deliver Full-Stack Capabilities 
Drive the design and development of user-facing experiences using modern frontend frameworks such as React, while shaping backend services and APIs built with C# and ASP.NET. Ensure frontend and backend systems are aligned, performant, and built for long-term maintainability. 

Financial Platform Trust 
Build and maintain software that processes financial transactions with a strong focus on correctness, traceability, and security. Ensure financial workflows are resilient, failures are handled predictably, and customer trust is protected. 

Production Reliability 
Own the reliability of the systems you contribute to by diagnosing production issues, improving observability, and strengthening operational practices that support stable releases and day-to-day platform health. 

Data and Performance at Scale 
Design and optimize relational data models and SQL queries that support high-volume production workloads. Balance performance, data integrity, and maintainability as systems evolve. 

Quality Engineering 
Write clean, maintainable, and well-tested code, applying shift-left practices such as unit and integration testing to catch issues early. Contribute to improving engineering standards, development workflows, and technical decision-making across the team. 

Cross-Functional Collaboration 
Partner closely with Product Managers, Designers, and Engineering peers to shape scope, assess trade-offs, and deliver well-defined solutions. Communicate clearly about technical constraints, risks, and progress to support predictable delivery. 

Who You Are 

• 8+ years of professional experience building and operating production SaaS software, with significant experience in full stack or backend-heavy roles. 

• Deep expertise in C# and ASP.NET, with a strong track record designing and evolving API-driven systems in distributed environments. 

• Strong grounding in object-oriented design, design patterns, and SOLID principles, with the ability to apply them pragmatically in large, evolving codebases. 

• Strong frontend experience building modern web applications using React, JavaScript, HTML, and CSS, with a focus on performance and usability. 

• Proven experience designing systems that operate at scale, including shaping architecture, defining service boundaries, and making sound trade-offs under real-world constraints. 

• Experience building or operating financial systems, payments platforms, or transaction-heavy applications where correctness, security, and traceability are critical. 

• Strong working knowledge of SQL and relational databases, including schema design, query optimization, and data integrity in high-volume production systems. 

• Experience working with cloud platforms (Azure preferred), including deploying, operating, and evolving services in production. 

• A disciplined approach to engineering quality, with experience applying shift-left testing practices, code review standards, and operational rigor to improve reliability. 

• Comfortable partnering with Product, Design, and Engineering peers to shape scope, assess trade-offs, and deliver outcomes in ambiguous problem spaces. 

• A clear, pragmatic communicator who can explain complex technical decisions and influence direction across teams. 

What We Offer 

• Competitive compensation 

• Meaningful health and dental benefits 

• Retirement savings support, including RRSP matching in Canada and 401(k) contributions in the U.S. 

• Professional development and continuing education opportunities 

• Hybrid and flexible work environment 
• Flexible PTO with close to 4 weeks of vacation and a company-wide holiday closure 
• Collaborative, supportive colleagues 

Salary Range - $100,000-150,000 

Note: We set standard base pay ranges for all roles based on function, level, and country location, benchmarked against similar stage growth companies. Final offer amounts are determined by multiple factors, including skills, depth of work experience and relevant licenses/credentials, and may vary from the amounts listed above.