Senior Software Engineer - Mainframe
Posted Sep 30, 2026 · We last checked this listing on Oct 6, 2026
Likely interview questions for this role
Written from this job description, not a generic list. Each one notes what the interviewer is really checking.
About your past
Tell me about a critical mainframe application you were the technical lead on. What did you own?
What they are checking: Whether they have truly led application support, not just worked tickets on it.
What DevOps practices have you brought to a mainframe team, and how did people react?
What they are checking: Whether they can lead modernization of how mainframe teams work, including winning people over.
Tell me about a time you explained a technical issue to a business user who was frustrated.
What they are checking: Whether they can communicate clearly with non-technical people during stressful moments.
What would you do
A junior developer's change caused a production incident. How do you handle it with them and the client?
What they are checking: Whether they protect the client, fix the problem and coach the developer without blame.
You get three urgent tickets at once from different users. How do you decide what comes first?
What they are checking: Whether they prioritize by business impact and communicate clearly with each requester.
How do you estimate the effort for an enhancement in an application you do not know well?
What they are checking: Whether they estimate honestly, include unknowns and update the estimate as they learn.
About the work
How would you design a COBOL change that touches CICS, DB2 and batch jobs so it can be rolled back safely?
What they are checking: Whether they think about end-to-end impact and rollback across connected parts of a system.
A DB2 query in a batch job suddenly runs ten times slower. How do you investigate?
What they are checking: Whether they understand access paths, statistics and EXPLAIN well enough to fix performance issues.
How have you used middleware like MQ to connect mainframe applications to other systems?
What they are checking: Whether they understand integration patterns that link mainframes to modern applications.
How do you review code from other developers on your team?
What they are checking: Whether they review with clear standards that catch risk before production.
How do you document an application so new team members can support it?
What they are checking: Whether they reduce the risk of knowledge living only in one person's head.
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Practice this out loudThe full job description
As published by Ensono.