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Guided design practice:System design questions Low-level and object-oriented design

fastprep / bank / stripe-q3 / P-201 - token-bucket rate limiterHOTseen 47x this week

Token-bucket rate limiterStripemedium12mdesign

Implement allow(ts) returning True if a request is permitted at unix ms ts for r req/s with burst up to b.

solution.pytests.txtnotes.mdpy 3.12 - 5.0ms

class RateLimiter:
    def __init__(self, r, b):
        self.r, self.b = r, b
        self.tokens, self.last = b, 0

    def allow(self, ts):
        # refill since last call
        self.tokens = min(self.b, self.tokens + (ts - self.last) * self.r)
        self.last = ts
        return self.tokens >= 1

passbasic_one_req_per_sec0.4ms

passburst_5_then_refill1.1ms

passmonotonic_timestamps0.9ms

passedge_ts_equal_last0.6ms

4 / 4 passed - 3.0ms total+ custom test

3,756

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369

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369 companies

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company

StripeDoorDashAirtable+366

stage

assessmentphoneonsitedesign

difficulty

easymediumhard

format

algorithmdatadesignproject

12 matchedfrom 3,756

59 topics

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Array

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Hash Table

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Simulation

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Greedy

607

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Math

386

Design

293

Graph

272

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252

Matrix

245

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181

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173

Concurrency

172

Prefix Sum

167

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161

Storage

147

Stack

130

Bank to Signal

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When tracked inboxes start seeing Stripe OAs land, the Q3 set surfaces to the top. You practice this quarter's questions, not the ones that were popular in 2019.

Problems get a HOT mark when an OA spikes in tracked inboxes.
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signal -> bank - last 7 dayslive

Stripe+12.4%promoted Q3 set47 pr

DoorDash+8.1%added 4 new problems32 pr

Anthropic+6.2%new cohort opened18 pr

Airtable+3.0%refreshed test cases28 pr

Adobe-2.1%lowered priority22 pr

Teslafrozenarchived19 pr

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FastPrep vs generic banks

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	FastPrep	Generic question banks
Company cohort tagging	Y	~
Runnable editor + inspectable tests	Y	~
Hiring-signal prioritization	Y	-
Post-pass approach review	Y	~

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