Stripe·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

Jun 2026

Summary

Stripe technical screen for a software engineering role. The whole thing centered on a single debugging scenario inside a custom HTTP library, and it went deeper than I expected for what felt like a contained problem.

Questions Asked (1)

You have a custom HTTP library where two test cases involving 301 redirects are failing. One involves a file stream and one involves binary content. The binary case times out at the post step. The call stack is deep and the helpers are barely commented. Walk through how you'd isolate the bug, write a minimal reproduction, and propose a fix that doesn't break the non-redirect paths.

Root Cause AnalysisAPI & IntegrationsTechnical Trade-offs

Author's notes

I spent probably the first five minutes just staring at the setup trying to figure out what I was even supposed to touch.

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AI HintsAI Generated

Suggested Approach

Start by reproducing the failures in isolation, then use binary search or logging to narrow down where the redirect handling diverges between the file stream and binary cases. Focus on the post-redirect step where the binary case times out, and compare the request construction and body handling for both content types. Propose a fix that conditionally handles redirects without altering the non-redirect code paths, and validate with targeted tests.

Pro tip: Demonstrate that you prioritize understanding the root cause over quick fixes by instrumenting the code with minimal, temporary logging and using a debugger to inspect the call stack. Also, mention that you'd check for known issues in the HTTP library's redirect handling, such as body rewind or content-length mismatches.

1. Reproduce and characterize the failures

Run the two failing tests in isolation and capture the exact error messages, stack traces, and timing. Note that the binary case times out at the post step, while the file stream case fails differently.

2. Trace the redirect flow and compare cases

Add temporary logging or use a debugger to trace the request lifecycle for both cases, focusing on how the body is handled before and after the 301 redirect. Identify where the binary case hangs.

3. Isolate the bug with a minimal reproduction

Create a small script that uses the library to perform a 301 redirect with a binary body, stripping away unrelated code. Confirm the timeout reproduces, then simplify further to pinpoint the faulty logic.

4. Propose a targeted fix

Based on the root cause (e.g., body not being rewound or content-length not updated), implement a fix that only affects redirect handling, such as resetting the stream or recalculating headers. Ensure non-redirect paths remain untouched.

5. Validate and prevent regressions

Run the original failing tests and the full test suite to confirm the fix works and doesn't break other scenarios. Add new tests for redirects with different body types to prevent future regressions.

Key Points to Mention

Use of binary search debugging to narrow down the faulty code segment
Importance of understanding the HTTP redirect semantics, especially 301 and body handling
Checking for stream rewindability and content-length consistency after redirect
Writing a minimal reproduction to isolate the issue from the full test suite
Ensuring the fix is scoped to redirect paths to avoid side effects
Adding regression tests for redirects with various body types

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