Principal Software Engineer

MainframeMaster; Newbury; On-site; GBP 80,000 - 100,000; Full time

Job summary

MainframeMaster is looking for a highly experienced Principal Software Engineer in Newbury, UK, to lead technical initiatives in the COBOL development ecosystem. This strategic role involves designing mission-critical infrastructure for global enterprises and collaborating with various teams to innovate at scale.

The ideal candidate should have over 10 years of software engineering experience, deep expertise in systems-level software, and a strong background in high-availability platforms. Join us to influence the future of modernization technologies!

Qualifications

• 10+ years of professional software engineering experience.
• Deep expertise in systems-level software and high-availability platforms.
• Strong background with COBOL and experience in complex initiatives.

Responsibilities

• Architect, design, and implement core components for COBOL tools.
• Drive modernization strategies for legacy application ecosystems.
• Collaborate with product management to shape roadmap priorities.

Skills

COBOL

C

C++

Systems-level software development

Leadership over technical initiatives

Cloud migration

Job description

# Principal Software EngineerRocket SoftwareFull-timeNewbury, United Kingdom0 viewsPosted June 5, 2026## Job DescriptionIt's fun to work in a company where people truly BELIEVE in what they're doing!Job Description Summary:The Infrastructure Modernization business unit is seeking a highly experienced Principal Software Engineer to join our engineering organization and provide deep technical leadership across our **COBOL** development ecosystem and our Enterprise Server application replatforming products. This is a hands-on, strategic role focused on designing, building, and evolving mission‐critical infrastructure used by global enterprises running high‐volume, high‐reliability systems.In this role, you will influence architecture across multiple product lines, guide engineering best practices, and help define the future of our platform as customers modernize decades‐old workloads into more agile, distributed and environments. You will partner closely with senior engineering leaders, product managers, and domain experts to drive innovation at scale.What You’ll DoTechnical LeadershipArchitect, design, and implement core components within our **COBOL** development tools, runtime environments, and mainframe replatforming infrastructure.Provide technical direction across multiple engineering teams building compilers, runtimes, middleware, and large-scale distributed systems.Drive modernization strategies for legacy application ecosystems, including **cloud** migration, workload transformation, and hybrid deployment scenarios.Hands-On EngineeringOwn complex technical domains end-to-end, from design through production, balancing long‐term architecture with immediate product needs.Build highly reliable, scalable, and secure infrastructure software used in mission‐critical enterprise environments.Conduct deep code reviews, troubleshoot production issues, and mentor engineers in system-level design and performance optimization.Cross-Functional ImpactCollaborate with product management to shape roadmap priorities and translate customer challenges into technical solutions.Work with System Test, DevOps, and release engineering to ensure high-quality, low‐risk releases across a diverse product portfolio.Introduce and champion engineering excellence practices, including automated testing, performance benchmarking, observability, and maintainability.What We’re Looking ForRequired Experience10+ years of professional software engineering experience, including leadership over complex, multi‐team technical initiatives.Deep expertise in systems-level software development, such as compilers, runtimes, operating systems, or infrastructure‐level platforms.Strong background in mission-critical, high‐availability software (e.g., financial services, telecom, government, or core enterprise platforms).Demonstrated experience with **COBOL**, PL/I, **C**, or **C**++—or significant experience in other lower-level languages with a willingness to dive into **COBOL** domain internals.Proven track record building or modernizing enterprise-grade tooling, middleware, or distributed systems.Ability to decompose legacy architectures, assess modernization paths, and design scalable solutions.Preferred QualificationsExperience with mainframe-to-**cloud** migration, workload replatforming, or runtime compatibility layers.Familiarity with Azure, **AWS**, or hybrid **cloud** architectures.Understanding of static and dynamic language runtimes, compiler pipelines, and virtual machine internals.Prior technical mentorship or architectural leadership spanning multiple scrum teams.Strong diagnostic skills for debugging low-level performance, memory, concurrency, or runtime issues.Who You AreA pragmatic engineer who balances ideal architecture with real-world constraints.Passionate about long-term maintainability and operational excellence.Comfortable working with legacy systems and excited about evolving them for the future.A collaborator who elevates teams through mentorship and cross-functional alignment.Someone who thrives in a technically rich, complex domain where your expertise has large-scale impact.Why Join Us?Influence the future of mission‐critical modernization technologies used worldwide.Work with a highly experienced engineering organization with deep domain expertise.Opportunity to shape architecture and product direction across multiple major portfolios.A culture that values technical depth, thoughtful engineering, and long-term product stewardship.#LI-Remote.Rocket Software Inc. is committed to creating a diverse environment and is proud to be an equal opportunity employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran status. Rocket Software Inc. is also committed to compliance with all fair employment practices regarding citizenship and immigration status.As part of our commitment to a safe and trustworthy workplace, we include background and reference checks in our hiring process.Rocket is committed to working with and providing reasonable accommodation to individuals with physical and mental disabilities. If you need special assistance or an accommodation while seeking employment, please call: 781-577-4321 or send an email to [e-mail]. We will make a determination on your request for reasonable accommodation on a case-by-case basis.If you like wild growth and working with happy, enthusiastic over-achievers, you'll enjoy your career with us!## How to ApplyApply directly through the application link above