eBay OA CodeSignal Breakdown | Process Review + High-Freq Questions

Recently, several of our students completed eBay Software Engineer / Data OAs. As a team that has been supporting eBay OA candidates for a long time, we immediately conducted a comprehensive review to systematically organize the process, question types, and pitfalls for students preparing for eBay or similar top tech OAs.

Overall, eBay's OA style is very typical:

• Does not pursue "fancy algorithms"
• But requires solid fundamentals, code robustness, and business understanding
• Belongs to the category of "looks easy, but easy to mess up"

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eBay OA Process Overview

Based on student feedback, most eBay tech OAs share these characteristics:

Dimension	Description
Platform	HackerRank / CodeSignal (Varies slightly by role)
Quantity	Usually 2 coding questions; some roles add SQL/Data questions
Duration	60 – 90 minutes
Language	Python / Java / C++ / JavaScript available
Complexity	Important, but "reasonable and stable" is more important

Summary: The core of eBay OA is not "do you know the optimal solution", but "do you code like a production engineer".

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eBay OA Real Question Examples

The following are examples of real question types that have appeared in eBay OAs. The questions themselves are not extremely difficult, but they emphasize rule comprehension, code stability, and detail handling.

Question 1: Array Segment Subtraction Simulation (Simulation + Greedy)

Core Problem Description

You are given numbers, an array of non-negative integers. Repeatedly find the leftmost non-zero element x, subtract x from consecutive elements to the right until subtraction is no longer possible, and add x to the final result. Return the total accumulated sum.

Key Points

• Patience and accuracy in simulation problems
• Strict understanding of "leftmost non-zero" and "stopping conditions"
• Correctly handling multiple iterations and array state changes

Python Reference Idea

def solve(numbers: list[int]) -> int:
    result = 0
    while True:
        # Find leftmost non-zero
        start = -1
        for i, v in enumerate(numbers):
            if v > 0:
                start = i
                break
        if start == -1:
            break

        x = numbers[start]
        result += x

        # Subtract x consecutively from start
        for j in range(start, len(numbers)):
            if numbers[j] >= x:
                numbers[j] -= x
            else:
                break

    return result

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Question 2: Case Count Difference (String Traversal)

Core Problem Description

Given a string consisting of uppercase and lowercase English letters, return the difference between the number of uppercase and lowercase letters.

Key Points

• Basic string traversal
• Familiarity with character ranges / ASCII / built-in functions
• Writing clear, readable, unambiguous implementation

Python Reference Implementation

def case_diff(s: str) -> int:
    upper = sum(1 for c in s if c.isupper())
    lower = sum(1 for c in s if c.islower())
    return upper - lower

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Question 3: Binary State + Operation Simulation (State Machine)

Core Problem Description

You are given a binary array state and a list of operations:

• "L": set the smallest index with value 0 to 1
• "C(index)": set state[index] = 0

Return the final state as a binary string.

Key Points

• Accuracy of state updates
• Ability to parse operation instructions
• Stable handling of "no-op" cases

Python Reference Implementation

import re

def process_ops(state: list[int], operations: list[str]) -> str:
    for op in operations:
        if op == "L":
            for i in range(len(state)):
                if state[i] == 0:
                    state[i] = 1
                    break
        elif op.startswith("C("):
            match = re.match(r"C\((\d+)\)", op)
            if match:
                idx = int(match.group(1))
                if 0 <= idx < len(state):
                    state[idx] = 0
    return ''.join(map(str, state))

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eBay OA FAQ (Mentor Q&A)

Q1: Is eBay OA difficult?

A: Not hard, but very "detail-oriented". It tests complete understanding of the problem and rigorous boundary conditions.

Q2: Is optimal solution (O(n) / O(log n)) required?

A: Not mandatory, but you must be able to "explain it". Usually O(n) or O(n log n) is sufficient. Brute force without complexity awareness will be penalized.

Q3: Will a small bug fail the OA?

A: Depends. Fatal logic errors are high risk. Small boundary errors might still allow passing to the next round, but tolerance is low.

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Need OA Support?

Our OA support focuses on:

• Rapid breakdown of questions and key points
• Stable, runnable, logic-tight implementation solutions
• Zero impact on accounts, devices, and subsequent interview processes

eBay truly differentiates candidates in the technical interviews and system discussions that follow, not the OA itself.

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