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314+ Oracle questions

Oracle interview questions and how to prepare

The questions candidates report from Oracle interviews, sorted by how often they come up, with difficulty and topics, plus original practice written in Oracle's interview style.

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ZorixOS tracks 314 community-reported Oracle interview questions, drawn from an open-source dataset of real interview reports and sorted by how frequently each one comes up. Every question links to its source. Alongside them are 78 original ZorixOS practice questions written in Oracle's known interview style (not claimed as asked at Oracle), so you can rehearse the real format. Practice any of them out loud in a free AI mock interview tuned to Oracle.

Updated July 2026

Oracle interview questions candidates report

Community-reported from real Oracle interviews (open-source dataset), most-asked first. Showing 60 of 314. Each links to its source.

  1. LRU Cache
    Hash TableLinked ListDesignDoubly-Linked List
    Medium100% asked
  2. Number of Islands
    ArrayDepth-First SearchBreadth-First SearchUnion-Find
    Medium100% asked
  3. Longest Substring Without Repeating Characters
    Hash TableStringSliding Window
    Medium89% asked
  4. Two Sum
    ArrayHash Table
    Easy83% asked
  5. Group Anagrams
    ArrayHash TableStringSorting
    Medium82% asked
  6. Sliding Window Maximum
    ArrayQueueSliding WindowHeap (Priority Queue)
    Hard79% asked
  7. Top K Frequent Elements
    ArrayHash TableDivide and ConquerSorting
    Medium79% asked
  8. Merge k Sorted Lists
    Linked ListDivide and ConquerHeap (Priority Queue)Merge Sort
    Hard75% asked
  9. Valid Parentheses
    StringStack
    Easy73% asked
  10. Diameter of Binary Tree
    TreeDepth-First SearchBinary Tree
    Easy73% asked
  11. Minimum Window Substring
    Hash TableStringSliding Window
    Hard73% asked
  12. Merge Intervals
    ArraySorting
    Medium72% asked
  13. Spiral Matrix
    ArrayMatrixSimulation
    Medium72% asked
  14. Minimum One Bit Operations to Make Integers Zero
    MathDynamic ProgrammingBit ManipulationRecursion
    Hard71% asked
  15. Longest Palindromic Substring
    Two PointersStringDynamic Programming
    Medium69% asked
  16. Meeting Rooms II
    ArrayTwo PointersGreedySorting
    Medium69% asked
  17. 3Sum
    ArrayTwo PointersSorting
    Medium66% asked
  18. LFU Cache
    Hash TableLinked ListDesignDoubly-Linked List
    Hard66% asked
  19. Reverse Linked List
    Linked ListRecursion
    Easy66% asked
  20. Search in Rotated Sorted Array
    ArrayBinary Search
    Medium66% asked
  21. Asteroid Collision
    ArrayStackSimulation
    Medium66% asked
  22. Container With Most Water
    ArrayTwo PointersGreedy
    Medium66% asked
  23. Find Leaves of Binary Tree
    TreeDepth-First SearchBinary Tree
    Medium66% asked
  24. Koko Eating Bananas
    ArrayBinary Search
    Medium66% asked
  25. Longest Mountain in Array
    ArrayTwo PointersDynamic ProgrammingEnumeration
    Medium66% asked
  26. Max Area of Island
    ArrayDepth-First SearchBreadth-First SearchUnion-Find
    Medium66% asked
  27. Merge In Between Linked Lists
    Linked List
    Medium66% asked
  28. Open the Lock
    ArrayHash TableStringBreadth-First Search
    Medium66% asked
  29. Remove All Adjacent Duplicates in String II
    StringStack
    Medium66% asked
  30. Sum Root to Leaf Numbers
    TreeDepth-First SearchBinary Tree
    Medium66% asked
  31. Longest Consecutive Sequence
    ArrayHash TableUnion-Find
    Medium65% asked
  32. Min Stack
    StackDesign
    Medium65% asked
  33. Find Valid Pair of Adjacent Digits in String
    Hash TableStringCounting
    Easy63% asked
  34. Minimum Absolute Difference
    ArraySorting
    Easy63% asked
  35. Rotting Oranges
    ArrayBreadth-First SearchMatrix
    Medium63% asked
  36. Valid Anagram
    Hash TableStringSorting
    Easy63% asked
  37. Trapping Rain Water
    ArrayTwo PointersDynamic ProgrammingStack
    Hard62% asked
  38. Design Authentication Manager
    Hash TableLinked ListDesignDoubly-Linked List
    Medium61% asked
  39. Lowest Common Ancestor of a Binary Tree
    TreeDepth-First SearchBinary Tree
    Medium61% asked
  40. Maximum Subarray
    ArrayDivide and ConquerDynamic Programming
    Medium61% asked
  41. Roman to Integer
    Hash TableMathString
    Easy61% asked
  42. Count Pairs Of Similar Strings
    ArrayHash TableStringBit Manipulation
    Easy60% asked
  43. Maximize Value of Function in a Ball Passing Game
    ArrayDynamic ProgrammingBit Manipulation
    Hard60% asked
  44. Binary Tree Zigzag Level Order Traversal
    TreeBreadth-First SearchBinary Tree
    Medium58% asked
  45. Decode String
    StringStackRecursion
    Medium58% asked
  46. Find Median from Data Stream
    Two PointersDesignSortingHeap (Priority Queue)
    Hard58% asked
  47. Generate Parentheses
    StringDynamic ProgrammingBacktracking
    Medium58% asked
  48. Longest Common Prefix
    ArrayStringTrie
    Easy58% asked
  49. All Ancestors of a Node in a Directed Acyclic Graph
    Depth-First SearchBreadth-First SearchGraph TheoryTopological Sort
    Medium58% asked
  50. Best Time to Buy and Sell Stock
    ArrayDynamic Programming
    Easy58% asked
  51. Binary Tree Right Side View
    TreeDepth-First SearchBreadth-First SearchBinary Tree
    Medium58% asked
  52. Count Distinct Numbers on Board
    ArrayHash TableMathSimulation
    Easy58% asked
  53. Count the Number of Houses at a Certain Distance I
    Breadth-First SearchGraph TheoryPrefix Sum
    Medium58% asked
  54. Count the Number of Houses at a Certain Distance II
    Graph TheoryPrefix Sum
    Hard58% asked
  55. Count Ways To Build Good Strings
    Dynamic Programming
    Medium58% asked
  56. Count Ways to Group Overlapping Ranges
    ArraySorting
    Medium58% asked
  57. HTML Entity Parser
    Hash TableString
    Medium58% asked
  58. Lucky Numbers in a Matrix
    ArrayMatrix
    Easy58% asked
  59. Minimize Length of Array Using Operations
    ArrayMathGreedyNumber Theory
    Medium58% asked
  60. Avoid Flood in The City
    ArrayHash TableBinary SearchGreedy
    Medium56% asked

These are the 60 most-reported of 314 tracked Oracle questions. Create a free account to drill the full set with solutions and an AI interviewer.

Practice questions in Oracle's style

Original ZorixOS questions written the way Oracle interviews, so you rehearse the real format. Not claimed as asked at Oracle.

  1. Imagine you're tasked with optimizing the performance of a critical Oracle Database query that's causing latency spikes for a major financial services client. Describe your systematic approach to identifying the bottleneck and potential solutions. Assume the query involves complex joins across several large tables.

    Software EngineerDatabase Performance TuningTests: Evaluates problem-solving skills, knowledge of database internals, and ability to handle high-impact performance issues.

  2. Oracle Cloud Infrastructure (OCI) offers various compute instance types. A customer is experiencing high CPU utilization on their application servers running on OCI, impacting performance. How would you diagnose whether this is a resource contention issue within OCI, an inefficient application code problem, or a network bottleneck, and what OCI tools would you use?

    Software EngineerCloud System DebuggingTests: Assesses understanding of cloud infrastructure, diagnostic tools, and systematic debugging in a distributed environment.

  3. You've identified a potential bug in the Oracle Fusion Applications' workflow engine that's causing incorrect approvals for expense reports. Outline your debugging strategy, including how you'd reproduce the issue, gather relevant logs, and propose a fix. Consider the complexity of a multi-tenant SaaS environment.

    Software EngineerSaaS Application DebuggingTests: Tests debugging skills in a complex enterprise SaaS application, including log analysis and understanding of multi-tenancy.

  4. Design a distributed caching layer for an Oracle SaaS application experiencing millions of read requests per second for user profile data. What are the key considerations for consistency, availability, and fault tolerance? Discuss potential technologies and trade-offs.

    Software EngineerSystem Design (Caching)Tests: Evaluates system design principles, distributed systems knowledge, and ability to design for scale and reliability.

  5. A customer reports intermittent failures when integrating their on-premises application with Oracle Integration Cloud (OIC). Describe how you would approach troubleshooting this integration, considering potential issues like network connectivity, authentication, message format transformations, and error handling within OIC.

    Software EngineerIntegration TroubleshootingTests: Probes troubleshooting skills for cloud integration services and understanding of common integration challenges.

  6. How would you design a system to detect and mitigate distributed denial-of-service (DDoS) attacks targeting Oracle's public cloud services? Consider strategies at the network edge, within the cloud infrastructure, and at the application layer.

    Software EngineerSystem Design (Security)Tests: Assesses understanding of security principles, distributed systems, and designing for resilience against attacks.

72+ more Oracle-style questions are in the free library, each practiceable live with adaptive follow-ups and an honest scorecard. Start free.

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Oracle Interview Questions (2026) | ZorixOS