Senior Full Stack Engineer - JavaScript / C#

Marmion Ltd; Hull and East Yorkshire; Hybrid; GBP 60,000 - 85,000; Full time

Benefits offered by this job

Free on-site Gym

Cycle to Work Scheme

Regular Social Events

Job summary

Marmion Ltd in Hull is seeking a Senior Full Stack Engineer to join a growing internal technology function across multiple sites. You will design, develop and support enterprise applications across backend and frontend technologies, helping standardise and modernise the technology estate.

The role involves migrating and enhancing existing applications, developing large-scale web portals, integrating business systems, and guiding colleagues through technical design and best practices.

Qualifications

• Strong commercial C# development experience.
• Experience building and supporting web applications.
• Understanding of both frontend and backend application architecture.
• Experience working with APIs, integrations and databases.
• The ability to operate across a varied technology landscape.

Responsibilities

• Designing, developing and supporting enterprise applications across backend and frontend technologies.
• Helping to standardise and modernise an evolving technology estate.
• Migrating and enhancing existing applications and platforms.
• Developing and maintaining large-scale web applications and customer-facing portals.
• Supporting integrations between business systems and web applications.
• Collaborating with developers across multiple technology stacks.
• Providing technical leadership and guiding less experienced engineers where required.
• Supporting ongoing innovation projects, including AI-enabled solutions and modern application development initiatives.
• Contributing to system architecture, technical design and engineering best practice.

Skills

C# development

Full stack

Architectural decisions

Mentoring

Problem solving

Tools

TypeScript

Node.js

.NET

SQL Server

Docker

Vite

KOA

Job description

This is a hands‑on role for an experienced engineer who enjoys solving complex technical challenges, influencing architecture decisions, and working across both backend and frontend technologies. You'll play a key role in helping modernise existing systems, supporting the migration of legacy applications, and contributing to the development of new enterprise‑scale platforms and web applications.

• Hull (office-based with flexibility for hybrid working)
• Free on-site Gym, Cycle to Work Scheme, Regular Social Events

The Opportunity

We’re searching for a Senior Full Stack Engineer to join a growing internal technology function across a multi-site group.

• Designing, developing and supporting enterprise applications across backend and frontend technologies.
• Helping to standardise and modernise an evolving technology estate.
• Migrating and enhancing existing applications and platforms.
• Developing and maintaining large-scale web applications and customer-facing portals.
• Supporting integrations between business systems and web applications.
• Working across databases, APIs and enterprise platforms.
• Collaborating with developers across multiple technology stacks.
• Providing technical leadership and guiding less experienced engineers where required.
• Supporting ongoing innovation projects, including AI-enabled solutions and modern application development initiatives.
• Contributing to system architecture, technical design and engineering best practice.

The successful candidate will have experience across a combination of the following technologies:

Core Technologies:

• TypeScript
• Node.js
• C#
• .NET

Databases:

• SQL Server
• Docker
• Vite
• KOA

We're looking for an engineer who can demonstrate:

• Strong commercial experience with C# development.
• Experience building and supporting web applications.
• Understanding of both frontend and backend application architecture.
• Experience working with APIs, integrations and databases.
• The ability to operate across a varied technology landscape.
• Strong problem-solving and technical decision-making skills.
• A collaborative approach and willingness to mentor and support colleagues.
• A passion for continuous improvement and modern software engineering practices.

What's in it for You?

• Opportunity to influence technical direction and architecture.
• Exposure to diverse, business-critical projects.
• Opportunity to work with modern cloud, web and integration technologies.
• Scope for growth and progression within an expanding technology function.