Stripe
6 questions · Coding · System design · Behavioral
Determine whether a string of brackets is balanced.
CodingApproachPush opens onto a stack; on a close, pop and match. Empty stack at the end means valid.
They look forStack intuition and handling of mismatched/empty edge cases.
Find the length of the longest substring without repeating characters.
CodingApproachSliding window with a set/last-seen map; advance the right edge, shrink the left on a repeat.
They look forTwo-pointer/sliding-window fluency and off-by-one care.
Design a rate limiter for a public API.
System designApproachCompare token bucket vs. sliding window, where state lives (per-node vs. Redis), and behavior under bursts.
They look forAlgorithm choice, distributed state, and failure/consistency trade-offs.
Design an idempotent payment API.
System designApproachIdempotency keys, exactly-once semantics, retries, and consistency under partial failure.
They look forCorrectness and safety in money-movement systems.
Model a ledger for double-entry accounting.
System designApproachImmutable entries, invariants that must always balance, and auditability.
They look forData modeling for correctness-critical domains.
Describe a project you are most proud of and your specific contribution.
BehavioralApproachAnchor to measurable impact; be crisp about what YOU did vs. the team, and the trade-offs you made.
They look forOwnership, impact, and honest self-attribution.
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