Oracle Java Interview Questions 2026
Published July 22, 2026 · Updated July 22, 2026
5 real Java interview questions asked at Oracle. Upvoted by engineers who cleared the loop. Covers Technical, System Design rounds.
5 questions
122 engineers asked
201 upvotes
Company: Oracle
Technology: Java
All Java Questions Asked at Oracle
Oracle
Hard
Technical round
PostgreSQLMySQLJava
Explain Oracle's redo log and undo log. How do they work together to provide crash recovery and read consistency? Walk through what happens when a transaction commits, then the server crashes, then restarts.
↑ 51 upvotes · 31 engineers asked this · SDE2
Oracle
Hard
System Design round
Distributed SystemsRedisJava
Design Oracle Cloud's IAM (Identity and Access Management) system. Thousands of customers, each with their own users, groups, and policies. How do you evaluate a permission check in under 10ms for every API call?
↑ 56 upvotes · 34 engineers asked this · SDE2
Oracle
Hard
Technical round
JavaDistributed Systems
Explain Oracle RAC (Real Application Clusters). How do multiple nodes access the same database storage? What is the Cache Fusion protocol? When would you choose RAC over a primary-replica setup?
↑ 44 upvotes · 27 engineers asked this · SDE2
Oracle
Medium
Technical round
3-6 yearsJava
Explain the difference between the young generation and old generation in JVM garbage collection. Why do most GC pauses come from minor (young-gen) collections rather than major ones, and when does that assumption break down?
↑ 29 upvotes · 16 engineers asked this · Senior SDE
Oracle
Medium
Technical round
1-5 yearsJava
Why must you override hashCode() whenever you override equals() in Java? What breaks if you only override equals()?
↑ 21 upvotes · 14 engineers asked this · Senior SDE
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Frequently asked questions
Explain Oracle's redo log and undo log. How do they work together to provide crash recovery and read consistency? Walk through what happens when a transaction commits, then the server crashes, then restarts.
Explain Oracle's redo log and undo log. How do they work together to provide crash recovery and read consistency? Walk through what happens when a transaction commits, then the server crashes, then restarts.
Design Oracle Cloud's IAM (Identity and Access Management) system. Thousands of customers, each with their own users, groups, and policies. How do you evaluate a permission check in under 10ms for every API call?
Design Oracle Cloud's IAM (Identity and Access Management) system. Thousands of customers, each with their own users, groups, and policies. How do you evaluate a permission check in under 10ms for every API call?
Explain Oracle RAC (Real Application Clusters). How do multiple nodes access the same database storage? What is the Cache Fusion protocol? When would you choose RAC over a primary-replica setup?
Explain Oracle RAC (Real Application Clusters). How do multiple nodes access the same database storage? What is the Cache Fusion protocol? When would you choose RAC over a primary-replica setup?
Explain the difference between the young generation and old generation in JVM garbage collection. Why do most GC pauses come from minor (young-gen) collections rather than major ones, and when does that assumption break down?
Explain the difference between the young generation and old generation in JVM garbage collection. Why do most GC pauses come from minor (young-gen) collections rather than major ones, and when does that assumption break down?
Why must you override hashCode() whenever you override equals() in Java? What breaks if you only override equals()?
Why must you override hashCode() whenever you override equals() in Java? What breaks if you only override equals()?