← Stripe Interview Insights

Stripe·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Stripe coding round with a KYC-themed problem. More parsing/validation logic than algorithms, which I wasn't fully expecting.

Questions Asked (1)

Q1

Given a list of customer records and a verification spec that defines which fields to check and what valid values look like (presence, format, allowed enum values, etc.), verify each record field by field and return per-record results showing which fields passed or failed and whether the record as a whole is valid.

Algorithms & Data StructuresAPI & IntegrationsTechnical Trade-offs
Author's notes

Took me a minute to internalize the spec-driven part.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements and edge cases, then propose a clean, extensible design that separates the verification spec from the validation logic. Walk through a concrete example to demonstrate correctness, and discuss trade-offs like performance, error handling, and scalability.

Pro tip: Emphasize that the spec should be data-driven (e.g., JSON schema) so that new fields or rules can be added without code changes, and mention that you'd return structured errors with field-level details for debugging and user feedback.

1. Clarify requirements and constraints

Ask about the expected input size, whether the spec is static or dynamic, and what the output format should be (e.g., per-field pass/fail, error messages). Confirm if partial validation is needed or if it should short-circuit.

2. Design the data structures

Define a VerificationSpec that maps field names to validation rules (e.g., required, type, format, enum). Define a RecordResult that contains a map of field names to validation results and an overall boolean.

3. Implement the validation logic

Iterate over each record and each field in the spec, applying the corresponding validator. Collect results per field, and determine overall validity by checking if all required fields passed.

4. Handle edge cases and errors

Consider missing fields, null values, type mismatches, and invalid formats. Decide whether to fail fast or accumulate all errors. Ensure the output includes clear error messages for each failed field.

5. Analyze complexity and trade-offs

Discuss time complexity (O(n*m) where n is number of records and m is number of fields) and space complexity. Mention potential optimizations like pre-compiling validators or parallel processing for large datasets.

Key Points to Mention

  • Data-driven spec design (e.g., using a schema or configuration) for extensibility
  • Separation of concerns: validation logic vs. spec definition vs. result reporting
  • Handling of edge cases: missing fields, nulls, type coercion, and format validation
  • Output structure: per-field results with error messages and overall record validity
  • Performance considerations: complexity, batching, and potential parallelization
  • Error accumulation vs. fail-fast strategies and their trade-offs

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