These are Data Structures questions of the kind Oracle actually asks — the patterns reported from Oracle's AI-engineering rounds, where design trade-offs, scale and failure modes matter as much as definitions. Treat this page as a mock interview: say every answer out loud before revealing it. If one surprises you, the lesson behind it is linked at the bottom.
Oracle Data Structures concept questions
Why do databases index with B-trees / B+ trees instead of binary search trees or hash indexes? When would a hash index actually win?
Asked in
Design a phone-directory lookup: 10 crore subscribers, queries are (a) exact number lookup and (b) 'list numbers starting with 98765'. One structure or two?
Asked in
Oracle Data Structures applied & hands-on questions
Sort a stack (largest on top) using only stack operations and recursion — no arrays, no explicit loops over indices. Trace it on [3, 1, 2] (top = 2).
Asked in
How to use this page: Oracle rarely asks something you've never seen — they ask a standard Data Structures concept and then push one level deeper ("why?", "what would you do if..."). Master the concept in the Data Structures course lessons, and the follow-up stops being scary.
Keep practising: Hash Tables, Linked Lists, Heaps and Choosing the Right Structure cover what most Oracle Data Structures rounds test.