Senior Mainframe Developer (Modernisation)

Job Description:

We are looking for a Senior Engineer with strong hands-on Mainframe development experience to join our engineering team.

This role will primarily focus on Mainframe application development, enhancement and support, while also contributing to the modernisation of existing applications and the development of future solutions using modern engineering technologies and practices.

The ideal candidate will have strong Mainframe development expertise, experience working with complex custom-built applications, and the ability to operate across both existing Mainframe solutions and modern technology platforms. Experience with, or a willingness to develop capabilities in, C#, .NET, REST APIs, SQL and Azure is highly desirable.

Key Responsibilities:

• Design, develop, enhance and support custom Mainframe applications.
• Perform hands-on development using COBOL, JCL, DB2 and batch-processing technologies.
• Analyse existing code, business logic, data flows and integrations to deliver enhancements and resolve complex technical issues.
• Take end-to-end ownership of application development, maintenance, troubleshooting and production stability.
• Perform root-cause analysis and implement sustainable solutions for application and production issues.
• Work across existing Mainframe applications and modernisation initiatives.
• Support integration between Mainframe applications and modern enterprise platforms.
• Contribute to modern application development using C#, .NET, REST APIs, SQL and cloud technologies.
• Help translate existing Mainframe functionality and business logic into modern solution designs as applications evolve.
• Collaborate with engineering, product and business teams to deliver reliable, scalable and maintainable solutions.
• Continuously build technical and functional knowledge across both Mainframe and modern technologies.

Required Skills & Experience:

• Strong hands-on experience in Mainframe application development.
• Proven experience in custom application development and enhancement, beyond production support and maintenance.
• Strong development experience with COBOL, JCL, DB2 and batch processing.
• Experience developing and maintaining complex, business-critical enterprise applications.
• Strong understanding of application architecture, business logic, integrations and data flows.
• Ability to analyse and modify complex business logic within mature applications.
• Strong debugging, troubleshooting and root-cause analysis capabilities.
• Experience supporting business-critical applications in production environments.
• Strong problem-solving skills, ownership mindset and learning agility.
• Ability to work effectively across legacy and modern technology environments.
• Strong communication and collaboration skills.

Preferred Experience:

• Experience with Mainframe modernisation or legacy transformation initiatives.
• Experience integrating Mainframe applications with modern platforms, services and APIs.
• Experience translating Mainframe functionality and business logic into modern application designs.
• Experience with C# and .NET.
• Experience with REST APIs and enterprise integration.
• Knowledge of SQL and modern data-access technologies.
• Exposure to modern frontend development technologies.
• Experience with Azure or other cloud platforms.
• Familiarity with Git, automated testing, CI/CD and DevSecOps practices.
• Experience using GitHub Copilot or other AI-assisted software development tools.
• Experience in warehouse, distribution, fulfilment or supply-chain applications is advantageous.

What We're Looking For:

We are looking for a strong Mainframe engineer with a modern engineering mindset. You should bring strong Mainframe development expertise while having the curiosity, learning agility and engineering mindset to work across both existing and modern technologies.

Skills

COBOL, JCL, Mainframes