Senior Full-Stack Software Engineer

Please note: 

Authorization to Work: Candidates must be legally authorized to work in the United States on a full-time basis. Mosaic is unable to engage in sponsorship or C2C for this role now or in the future.

Geographic flexibility: This position is open to candidates residing anywhere in the US with a strong preference in the surrounding Seattle, WA area. 

Occasional travel to client sites within the U.S may be required, up to 25%. 

This role requires a minimum of 8+ years of hands-on development experience.

Senior Full-Stack Software Engineer

We are seeking a Senior Full-Stack Software Engineer to contribute to the architecture, design, and delivery of modern web applications. This role is ideal for a hands-on senior developer who enjoys solving complex technical problems, building across the stack, and partnering with product, design, data science, and engineering teams to deliver secure, scalable, cloud-native software.

You will contribute across the full stack from Svelte frontend applications to .NET/C# backend services, APIs, SQL databases, and Azure infrastructure while helping shape implementation approach, supporting engineering standards, mentoring teammates, and making thoughtful technical decisions that balance speed, quality, and maintainability.

We value depth in Svelte, .NET/C#, and SQL more than equal expertise across every technology in the stack. Experience with adjacent tools such as Python and additional Azure services is valuable, but candidates are not expected to be equally deep in every area on day one.

Roles and Responsibilities

Design, build, and deliver full-stack applications using Svelte, .NET/C#, SQL, and Azure

Contribute hands-on to daily development across frontend, backend, APIs, and data layers

Help guide technical design, implementation approach, and engineering best practices

Review code, mentor junior engineers, and support overall code quality and maintainability

Design and optimize APIs, services, data models, and relational databases in SQL Server and PostgreSQL

Improve CI/CD pipelines and support Azure deployment, monitoring, and production operations

Partner with product, design, data science, and client stakeholders to turn requirements into effective technical solutions

Contribute to technical planning, documentation, troubleshooting, and continuous improvement across projects

Skills and Experience

8+ years of professional experience building and delivering full-stack software in production environments

Strong hands-on experience with Svelte, .NET/C#, and SQL, including relational database design and performance optimization in SQL Server and PostgreSQL

Experience building and deploying applications on Azure

Proven experience designing and building RESTful APIs, authentication and authorization flows, and secure cloud-based systems

Strong system design skills and the ability to contribute to architecture and technical direction

Experience delivering software in enterprise, consulting, or other complex production environments

Familiarity with Python and comfort working in a multi-language environment

Familiarity with AI-enabled application features or AI-assisted development workflows

Strong written and verbal communication skills, with the ability to work effectively across technical and non-technical teams

Demonstrated ability to mentor other engineers, review code, and deliver high-quality work on schedule

Preferred Qualifications

Experience with Docker, Kubernetes, microservices, and event-driven architectures

Familiarity with AI/ML integrations, data pipelines, or intelligent application features

Experience improving deployment processes, observability, and operational resilience

Strong understanding of accessibility standards, usability principles, and modern UI/UX patterns

Education

Bachelor’s degree in Computer Science or a related field, or equivalent practical experience

At Mosaic, we are invested in our people and are proud to offer a competitive total compensation package. Compensation decisions are made based on a variety of factors, including but not limited to relevant skills, consulting experience, education and training, demonstrated competencies, geographic location, and other business and organizational needs. The salary range listed reflects a good faith estimate of the compensation for this role at the time of posting. A reasonable national base salary range for this position is $115,000.00 - 175,000.00 USD annually, and compensation decisions are dependent on the facts and circumstances of each case. This position is eligible to participate in a bonus program of up to 10% of annual compensation, subject to individual and organizational performance. In addition to salary and bonus eligibility, Mosaic offers a comprehensive benefits package, including health and wellness benefits, a Flexible Time Off program, paid holidays, a discretionary 401(k) match, and for US based employees, participation in the Employee Stock Ownership Plan (ESOP).

We regularly review our compensation practices to ensure they remain competitive, compliant, and aligned with our values. Additional details on Mosaic’s benefit package can be found at the following LINK.