21 questions · from 2 interviews

Interactive Brokers interview questions

Every question candidates reported from their Interactive Brokers interviews, most frequently asked first. Each links to the write-up it came from, so you can see the round and how it went.

Interactive Brokers coding and DSA questions

  1. 01

    Delete Node in Singly Linked List (O(1))

    Given a node in a singly linked list (not the head), delete it in constant time.

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  2. 02

    Find Second Maximum Element in Array (One Pass, O(1) Space)

    Find the second maximum element in an array using a single pass and constant extra space.

    Easy · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  3. 03

    Check Number Presence in Integer Stream (O(1) Time/Space)

    A large stream of integers flows into a queue throughout the day, with the constraint that the difference between consecutive numbers is always 1. At the end of the day, answer queries asking whether a specific number x appeared in the stream, with the…

    Hard · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  4. 04

    Minimize Difference Between Two Array Sums

    Given an array, divide its elements into two subarrays such that the absolute difference between their sums is minimized.

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  5. 05

    Comparator vs. Comparable and DSA Application

    Discuss the difference between Java's Comparator and Comparable interfaces. Be prepared to solve a Data Structures & Algorithms (DSA) question using either of these.

    From Interactive Brokers | Backend Developer | Interview Experience | July 2025

  6. 06

    HashMap Internals and Custom Equals/HashCode

    Explain the internal working of Java's HashMap. Demonstrate how to implement equals() and hashCode() methods for a custom class to ensure correct behavior when used as a key in a HashMap.

    From Interactive Brokers | Backend Developer | Interview Experience | July 2025

Interactive Brokers system design questions

  1. 01

    Database Types and Technologies

    Discuss the differences between relational and non-relational databases. Explain MongoDB and Redis, and discuss why Redis, despite its speed, is typically not used as a primary database for large-scale systems.

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

Interactive Brokers other questions

  1. 01

    OOP: Parent p = new Child() and Child c = new Parent()

    Explain the concepts behind Parent p = new Child() and Child c = new Parent(), including reasoning for valid/invalid assignments and polymorphism in Java.

    From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  2. 02

    OOP: Object Typecasting

    Explain typecasting in Java objects.

    From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  3. 03

    Java: Lambda Functions

    Explain lambda functions in Java.

    From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  4. 04

    Java: Streams API

    Explain the Streams API in Java.

    From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  5. 05

    Java: Serializable Interface

    Explain the Serializable interface in Java.

    From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  6. 06

    Java HashMap Internals

    Explain the internal workings of Java's HashMap, including how key-value pairs are stored, load factor, rehashing, and collision handling (before and after Java 8).

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  7. 07

    Custom Object as HashMap Key (equals() and hashCode())

    Design a Student class with name, id, and marks attributes. Discuss if this class can be directly used as a key in a HashMap. Explain the default equals() and hashCode() implementations, why overriding them is necessary for logical equality when using custom…

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  8. 08

    Java Comparable vs Comparator

    Explain the differences between Comparable and Comparator interfaces in Java. Demonstrate implementing Comparable and creating a Comparator for a different sorting strategy. Explain the meaning of the return values -1, 0, and 1.

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  9. 09

    SQL & Database Concepts

    Explain different types of SQL joins, database indexing, and the data structures commonly used in indexing (e.g., B-Trees).

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  10. 10

    25 Horses and 5 Tracks Puzzle

    Given 25 horses and 5 tracks, find the top three fastest horses. You can only race 5 horses at a time and have a stopwatch. There is no way to tell the speed of the horses, only their relative order in a race. What is the minimum number of races required?

    Hard · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  11. 11

    2 Eggs and 100 Floors Puzzle

    You have 2 identical eggs and a 100-story building. You want to find the highest floor from which an egg can be dropped without breaking. What is the minimum number of drops in the worst-case scenario?

    Hard · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  12. 12

    Maximize Black Ball Probability Puzzle

    Given 50 black balls and 50 white balls, distribute them into two bags to maximize the probability of drawing a black ball when randomly selecting a bag and then drawing a ball from it.

    Medium · From Interactive Brokers Junior Software Engineer role Interview Experience. (13.5 LPA CTC )

  13. 13

    Camel and Bananas Puzzle

    Solve the classic 'Camel and Bananas' puzzle. This typically involves a camel, a certain number of bananas, and a destination, with rules about how many bananas the camel can carry and how many it eats per unit of distance.

    From Interactive Brokers | Backend Developer | Interview Experience | July 2025

  14. 14

    SOLID Principles Discussion

    Discuss and explain the SOLID principles of object-oriented design.

    From Interactive Brokers | Backend Developer | Interview Experience | July 2025

Interactive Brokers interview questions FAQ

What questions are asked in Interactive Brokers interviews?

Candidates reported 21 distinct questions across 2 Interactive Brokers interviews. 6 coding and DSA questions, 1 system design questions, 14 other questions.

How difficult are Interactive Brokers interview questions?

Of the questions candidates rated, 8% were easy, 67% medium and 25% hard.