Walmart Labs·Software Engineer·Technical Phone Screen·Senior

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May 2026

Summary

Walmart Labs code review round where you get four files of deliberately bad code and about ten minutes to tear them apart. The breadth vs depth tradeoff is real and stressful.

Questions Asked (1)

You are given four source files with intentionally poor code. In roughly ten minutes, review all of them and identify the most critical issues across correctness, security, concurrency, performance, and readability. Prioritize by impact and propose concrete fixes.

Technical Trade-offsRoot Cause AnalysisSystem Design

Author's notes

Ten minutes for four files sounds manageable until you're actually in it.

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AI HintsAI Generated

Suggested Approach

Start by skimming all four files to get a high-level understanding, then dive into each one focusing on the most critical issues first. Prioritize issues by impact (e.g., security vulnerabilities, correctness bugs, concurrency deadlocks) and propose concrete fixes with trade-offs. Communicate your findings clearly, grouping by category and severity.

Pro tip: While reviewing, verbalize your thought process and explicitly state the impact of each issue (e.g., 'This SQL injection could lead to data breach'). Also, mention how you would test or verify the fixes, showing a proactive quality mindset.

1. Rapid Skim and Categorize

Quickly scan all files to identify the languages, frameworks, and apparent purpose. Note any obvious red flags like hardcoded secrets, commented-out code, or TODO markers.

2. Deep Dive by Priority

Focus on one file at a time, starting with the most critical issues: security (injection, auth flaws), correctness (logic errors, edge cases), concurrency (race conditions, deadlocks), performance (inefficient algorithms, N+1 queries), and readability (naming, structure).

3. Prioritize and Propose Fixes

For each issue, assess its impact (e.g., data loss, security breach, crash) and likelihood. Propose specific, actionable fixes, mentioning trade-offs (e.g., adding a lock may reduce performance).

4. Communicate Findings

Structure your response by category and severity, using clear examples from the code. Explain the 'why' behind each issue and how your fix addresses it, demonstrating root cause analysis.

Key Points to Mention

Security: SQL injection, XSS, insecure deserialization, hardcoded credentials, improper authentication/authorization.
Correctness: Off-by-one errors, null pointer exceptions, unhandled edge cases, incorrect error handling.
Concurrency: Race conditions, deadlocks, lack of synchronization, thread-safety issues.
Performance: Inefficient algorithms (e.g., O(n^2)), unnecessary database queries (N+1), memory leaks, blocking I/O.
Readability: Poor naming, lack of comments, overly complex functions, inconsistent formatting, magic numbers.
Testing and Verification: How to write tests to catch these issues, use of static analysis tools, code reviews.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.