Mainframe Developer

Oorwin AI; St. Louis (MO); Remote; USD 117,000 - 234,000; Full time

Job summary

Oorwin AI is seeking a Senior Mainframe Developer to investigate and remediate security vulnerabilities in production banking systems. You will work hands-on with COBOL, CICS, DB2, and z/OS to trace vulnerabilities to their root cause and implement secure fixes without disrupting critical operations.

The role demands strong problem-solving skills, the ability to work independently in high-stakes environments, and collaboration with security, infrastructure, and application teams to validate

Qualifications

• Requires deep knowledge of mainframe architecture and legacy banking systems.
• Experience with secure coding practices in mainframe environments.
• Proven ability to remediate vulnerabilities in production-critical systems.

Responsibilities

• Investigate and analyze security vulnerabilities within legacy mainframe banking applications.
• Trace issues to root cause and design secure remediation strategies.
• Modify and enhance COBOL, CICS, and DB2 codebases while preserving production stability.
• Collaborate with security, infrastructure, and application teams to validate fixes.
• Conduct secure coding reviews and enforce mainframe security best practices.
• Document remediation steps, secure design patterns, and operational improvements.
• Strengthen long-term resilience of legacy banking systems.

Skills

COBOL

CICS

DB2

z/OS

Secure coding

Job description

Position: Mainframe Developer (Senior – Security Remediation)

Location: Remote

Duration: 6-12+ Months Contract

Role Overview

We are seeking experienced Senior Mainframe Engineers with deep expertise in legacy banking systems to investigate, understand, and safely remediate security vulnerabilities in production‑critical applications. This role requires strong proficiency in COBOL, CICS, DB2, and z/OS, along with the ability to navigate complex, decades‑old financial systems where stability and accuracy are paramount. The ideal candidate will be a hands‑on engineer who can trace vulnerabilities to their root cause, implement secure fixes, and ensure safe deployment without disrupting mission‑critical banking operations.

Key Responsibilities

• Investigate and analyze security vulnerabilities within legacy mainframe banking applications.
• Trace issues to their technical root cause and design secure remediation strategies.
• Modify and enhance COBOL, CICS, and DB2 codebases while ensuring production stability.
• Collaborate with security, infrastructure, and application teams to validate fixes.
• Conduct secure coding reviews and enforce mainframe security best practices.
• Document remediation steps, secure design patterns, and operational improvements.
• Contribute to strengthening long‑term resilience of legacy banking systems.

Required Skills

• Deep understanding of mainframe application architecture and legacy banking systems.
• Hands‑on experience with secure coding practices in mainframe environments.
• Proven ability to remediate vulnerabilities in production‑critical systems.
• Strong problem‑solving skills and ability to work independently in high‑stakes environments.

Preferred Skills

• Experience with large‑scale financial or banking applications.
• Familiarity with mainframe modernization initiatives.
• Exposure to secure SDLC practices and vulnerability management frameworks.
• Strong communication skills to bridge security and engineering teams.