Coinbase
5 questions · Coding · System design
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.
EvaluatesStack intuition and handling of mismatched/empty edge cases.
Return the k-th largest element in an unsorted array.
CodingApproachA size-k min-heap, or quickselect for average O(n); discuss the trade-offs.
EvaluatesHeap vs. selection trade-offs and awareness of average vs. worst case.
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.
EvaluatesAlgorithm choice, distributed state, and failure/consistency trade-offs.
Design a URL shortener (like TinyURL).
System designApproachTalk through the API, a hash/base-62 key scheme, storage and read/write ratio, caching hot links, and redirects.
EvaluatesScoping, key generation, read-heavy scaling, and caching decisions.
Tell me about a time you failed and what you changed afterward.
BehavioralApproachPick a real failure, own it without blaming others, and show the concrete lesson you applied later.
EvaluatesSelf-awareness, accountability, and growth.
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