Top 45
Prep plan
Updated weekly · Last refresh Aug 30

Decagon Software Engineer Interview Questions

The questions to prepare for a Decagon Software Engineer interview. Questions from real interview reports rank first. Updated weekly.

45questions
~7htotal time
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1
CodingStart here. 19 questions · ~175 min
First Non-Repeating CharacterEasy
Practice

Find the first non-repeating character in a string using frequency counting and a second pass in O(n) time.

Hash TablesStringsSearchingDecagon
Maximum Sum Contiguous SubarrayEasy
Practice

Use Kadane's algorithm to find the contiguous subarray with the largest sum in linear time.

Dynamic ProgrammingArraysGreedyDecagon
Reverse String In PlaceEasy
Practice

Reverse a string using a two-pointer approach by converting it to a mutable character list in Python.

CodingStringsProgrammingDecagon
Cycle Detection in Linked ListMedium

Tests knowledge of standard linked list cycle detection algorithms and correctness reasoning.

Basic AlgorithmsLinked ListsTwo PointersDecagon
Queue With Two StacksMedium

Tests data structure implementation and your understanding of amortized time complexity.

StackQueuefunctionsDecagon
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2
Behavioral & Leadership24 questions · ~221 min
Explaining Python and SQL ImpactEasy

Tests how clearly you communicate hands-on Python and SQL experience through a concrete example with ownership and measurable impact.

sqltechnical experiencepythonDecagon
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3
More topics2 questions · ~18 min
Design Low-Latency MessagingHard

Tests system design tradeoffs for persistence, latency, and scalability.

Feature StoreModel ServingRecommendation SystemsDecagon
Relational vs Non-RelationalEasy

Tests understanding of database models and when to use each.

SubqueriesJoinsData WranglingDecagon

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Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
The finish line: interview-readyComplete all 45 questions plus 3 hands-on drills to finish this plan.