Problem Bank - 4,280 interview problems

Practice the problems
companies are actually asking.

Company-scoped practice from 392 companies, spanning online assessments, phone screens, onsite interviews, system design, low-level design, and project coding.

Open the bank See a problem

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

4,280

practice problems

+1,444 / 30d

392

companies covered

+133 / 30d

topics covered

across all formats

practice formats

coding - data - design - project

392 companies

Browse by the company you are applying to.

Every problem is tagged with company and cohort, so practice follows your target list instead of a generic topic shuffle.

688problems

266problems

155problems

123problems

108problems

108problems

107problems

A run-through

Scope / Solve / Review.

Three minutes inside the bank.

bank - filter4,280 -> 12

company

StripeDoorDashAirtable+389

stage

assessmentphoneonsitedesign

difficulty

easymediumhard

format

algorithmdatadesignproject

12 matchedfrom 4,280

59 topics

Mapped to the skills companies actually ask.

Topic heat reflects its frequency across every practice format.

Array

1,512

Hash Table

924

String

843

Simulation

796

Sorting

686

Greedy

644

Dynamic Programming

448

Math

429

Design

335

Graph

319

Consistency

293

Matrix

276

Binary Search

247

Depth First Search

225

Data Modeling

224

Heap

210

Two Pointers

209

Breadth First Search

208

Concurrency

203

Sliding Window

194

Tree

191

Prefix Sum

179

Storage

179

Stack

154

Bank to Signal

The bank knows what is being asked right now.

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.
Each company set is dated and prioritized by freshness.
Frozen cohorts drop in priority so you do not waste reps.

See live signals

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

auto-curated - refreshed hourly

FastPrep vs generic banks

Practice by target, not by folklore.

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

Practice the set before it hits you.

Open the bank, pick your target company, and run the exact style of OA you are likely to see this week.

Open Problem Bank Start free