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Stripe·Software Engineer·Online Assessment (OA)·Intermediate

Intermediate
Jul 2026

Summary

Stripe software engineer round that was basically a CSV parsing problem dressed up as a payments exercise. Sounds mundane but the edge case handling is where it gets you.

Questions Asked (1)

Q1

Given a CSV file of payment transactions with a status field and various amount/fee columns, parse the file and output a fee report grouped by payment status. The output format must be byte-exact, matching a provided example including column order, separators, header, alignment, decimal precision, and trailing newline.

Algorithms & Data StructuresTechnical Trade-offsAPI & Integrations
Author's notes

The actual math is nothing.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the exact output format and edge cases (e.g., missing values, special characters) before writing any code. Then design a solution that parses the CSV, aggregates fees by status, and formats the output with precise control over alignment, separators, and decimal precision. Finally, validate the output against the provided example byte-for-byte.

Pro tip: Use a CSV library with proper quoting and escaping to handle edge cases, and format numbers using fixed-point arithmetic to avoid floating-point rounding errors. Always test with the provided example and compare byte-by-byte to catch subtle formatting issues.

1. Clarify Requirements and Edge Cases

Ask about the exact output format, including column order, separators, header text, alignment, decimal precision, and trailing newline. Discuss how to handle missing or malformed data, and whether fees should be summed or averaged.

2. Design the Parsing and Aggregation Strategy

Choose a robust CSV parsing approach (e.g., using a library) and decide on data structures to group fees by status. Consider using a dictionary mapping status to aggregated fee totals, and handle numeric precision carefully.

3. Implement Precise Output Formatting

Construct the output string by explicitly formatting each column with the required alignment and decimal precision. Use string formatting functions that allow control over padding and rounding, and ensure the trailing newline is included.

4. Validate Against the Example

Run your solution on the provided example and compare the output byte-by-byte with the expected result. Use diff tools or checksums to catch any discrepancies, and iterate until they match exactly.

5. Discuss Trade-offs and Scalability

Explain your choices regarding parsing libraries, memory usage, and performance. Mention how your solution would scale with larger files and whether streaming or batch processing is appropriate.

Key Points to Mention

  • Use of a CSV parsing library to correctly handle quoted fields, commas within values, and newlines.
  • Aggregation of fees by status using a hash map or dictionary, with careful handling of missing or non-numeric values.
  • Formatting numbers with fixed decimal places using integer arithmetic or decimal libraries to avoid floating-point errors.
  • Exact string formatting for alignment (e.g., left-align status, right-align amounts) and consistent separators.
  • Inclusion of a trailing newline at the end of the output.
  • Testing strategy: byte-by-byte comparison with the provided example, and consideration of edge cases like empty input or unknown statuses.

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