Stripe·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

May 2026Remote

Summary

Stripe coding screen, one question about building a subscription renewal reminder scheduler. Pretty focused on getting the filtering and sorting logic right under time pressure.

Questions Asked (1)

Implement a function that takes a list of subscriptions with expiry dates, a current date, and a lookahead window, then returns the IDs of subscriptions expiring within that window, sorted by expiry date then ID.

Algorithms & Data StructuresAPI & Integrations

Author's notes

I fumbled the sort order at first.

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AI HintsAI Generated

Suggested Approach

Clarify the input format and edge cases (e.g., date inclusivity, time zones) before coding. Then outline an algorithm: filter subscriptions where expiry is within [current, current+window], sort by expiry then ID, and return IDs. Discuss time/space complexity and potential optimizations.

Pro tip: Mention that in production systems like Stripe, you'd likely use a database query with an index on expiry date to avoid loading all subscriptions into memory, and handle time zones carefully.

1. Clarify requirements and edge cases

Ask about date format, inclusivity of window boundaries, time zones, and whether the input list is sorted. Confirm expected output format.

2. Design the algorithm

Filter subscriptions where expiry is >= current date and <= current date + window. Then sort the filtered list by expiry date ascending, and for ties, by ID ascending.

3. Analyze complexity and optimizations

State time complexity: O(n log n) due to sorting, where n is number of subscriptions. Mention that if the list is already sorted by expiry, filtering can be O(n) and no sort needed.

4. Implement and test

Write clean code with meaningful variable names. Walk through a few test cases including empty list, no expiring subscriptions, and boundary conditions.

Key Points to Mention

Date handling: use appropriate date library or timestamps, consider time zones and daylight saving.
Inclusivity of the lookahead window: clarify if the end date is inclusive or exclusive.
Sorting stability and tie-breaking: sort by expiry then ID to ensure deterministic order.
Time and space complexity: O(n log n) time, O(n) space for filtered list.
Potential optimization: if input is sorted by expiry, use binary search to find range and avoid full sort.
Production considerations: database indexing, pagination, and avoiding loading all data into memory.

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