Maintenance and operations of An insurance company’s core system

While working at Nomura Research Institute, I was assigned to the system maintenance and operations team for an insurance company with over 900,000 active contracts.

The system comprised COBOL batch processes, a Java-based web application, and an Oracle Database, and also included maintenance of Windows Server 2000 running Apache and Tomcat.

My role was to coordinate with external vendors and ensure system quality.

In my first year, after completing six months of in-house training, I contributed to both client revenue and internal efficiency by modifying existing screens (from detailed design to testing), developing new batch processes, and building internal Excel automation tools.

I gained hands-on experience with Java, JSP, and COBOL through these tasks.

From the second year, I focused on reviewing design documents created by vendors and developing test cases to ensure design quality.

Through practical work, I gained balanced experience across both upstream and downstream phases of the waterfall development model.

This allowed me to work comprehensively on a large-scale core system and deepen my understanding of robust and secure system design.

I developed foundational skills in front-end and back-end technologies, as well as infrastructure, establishing a strong base as a full-stack engineer.

• Maintained and operated a robust and secure system for approximately two years, which supported over 900,000 active contracts and was composed of COBOL batch processes, a Java-based web application, Oracle Database, and Windows Server 2000 with Apache and Tomcat.
• Discovered hidden bugs through code reviews and fixed them proactively before they could affect the system.
• Developed internal automation tools using Excel VBA, contributing to improved operational efficiency.
• Deepened my knowledge of system development through six months of in-house training and by obtaining multiple national IT certifications in Japan, including the Fundamental Information Technology Engineer Examination, Applied Information Technology Engineer Examination, and Database Specialist certification.