Pinterest Interview Questions

Pinterest Interview Questions

Practice 145 real Pinterest interview questions for 2026. Covers all top categories — Coding & Algorithms, Data Manipulation (SQL/Python), Analytics & Experimentation, Machine Learning, System Design — across Data Scientist, Software Engineer, Machine Learning Engineer, and Data Analyst roles. Real questions from actual interviews with detailed solutions. This collection leans hard on coding and algorithm problems for SWE candidates while giving equivalent weight to experiment design, SQL/Python analytics, and model evaluation for data roles, making it a focused resource for interview preparation for screens, virtual onsites, and take-home assignments. Expect interviews to evaluate algorithmic thinking, production design, experimental rigor, and clear data storytelling. For Data Scientists you’ll see carousel and billboard lift evaluation, weighted/random-sampling implementations, numpy/pandas and SQL analytics on category and video-time metrics, and survey-balance diagnostics. Software Engineers face prefix-matching, catalog update pipelines, sparse-matrix ops, grid/graph puzzles, and ads event reporting or blob storage design. Machine Learning Engineers get pin-search and recommender design, Naive Bayes/bagging implementation, hyperparameter generation, and sampling-by-score problems. Data Analysts encounter cohort and cancellation/rebooking metric questions. Prepare with timed coding drills, end-to-end A/B case studies, polished Python/SQL practice, and concise STAR stories for behavioral rounds.

145 Questions 1 Company07.23.2026
Showing 20 results
Role
Pinterest logo
Pinterest
Medium
Machine Learning EngineerSenior+ Locked

Solve Expression and Tree-List Problems

This question evaluates competency in string expression generation under a custom left-to-right evaluation rule and in-place binary search tree manipu...

Coding & Algorithms
15
0
108 people solved
Feb 21, 2026
Pinterest logo
Pinterest
Hard
Machine Learning Engineer

Insert parentheses to minimize expression value

You are given a string expression of the form A+B, where A and B are non-empty strings of digits (no digit is '0'). You must insert exactly one pair o...

Coding & Algorithms
6
1
115 people solved
Feb 9, 2026
Pinterest logo
Pinterest
Medium
Data Scientist Locked

Implement Jackknife and Random Choice

This question evaluates understanding of statistical resampling (jackknife), probabilistic sampling algorithms including with- and without-replacement...

Coding & Algorithms
8
0
91 people solved
Jan 11, 2026
Pinterest logo
Pinterest
Medium
Data Analyst

Compute percent of first-cancelled users who never rebook

You are interviewing for a health-tech product analytics role. Assume the following table contains one row per appointment with its final status. Tabl...

Data Manipulation (SQL/Python)
7
0
48 people solved
Nov 22, 2025
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Pinterest
Easy
Data Analyst

Compute percent of first-cancel users who never return

You’re analyzing appointment behavior for a scheduling product. Table appointments - appointment_id (STRING, PK) - user_id (STRING) - scheduled_start_...

Data Manipulation (SQL/Python)
3
0
25 people solved
Oct 26, 2025
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Pinterest
Medium
Data Scientist

Find top category by video time spent

Pandas required. You are given a DataFrame df with columns: user_id (int), pin_id (int), pin_type (str), category (str or None), time_spent_sec (numer...

Data Manipulation (SQL/Python)
18
0
140 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Implement and extend My Calendar III

Design and implement a booking system like LeetCode 732 (My Calendar III). Provide a class with methods: book(start, end) using half-open intervals [s...

Coding & Algorithms
6
0
102 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Write SQL to compute max-overlap lists

Invented schema and sample data below. Assume 'today' is 2025-09-01 and 'last 7 days' means 2025-08-26 through 2025-09-01 inclusive. Only consider lis...

Data Manipulation (SQL/Python)
0
0
9 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Find list pair with maximum overlap

You are given N labeled lists of items as a Python dict mapping list_name -> iterable of strings. Example input: {'L1': ['A','B','C'], 'L2': ['A','C',...

Coding & Algorithms
5
0
90 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Transform nested dicts with pandas apply/lambda

Given a pandas DataFrame df with columns: user_id (int), ts (datetime64[ns]), events (list of dicts), attrs (dict). Example rows (conceptual): user_id...

Data Manipulation (SQL/Python)
0
0
5 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Write windowed retention and ARPU SQL

You are given three tables. Write one SQL script (CTEs allowed) that answers all parts using window functions and joins (no procedural loops): Schema:...

Data Manipulation (SQL/Python)
1
0
3 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Write SQL to rank categories by impressions

You are given the following schema and sample data. Today is 2025-09-01. Schema: - users(user_id INT, country_id VARCHAR) - countries(country_id VARCH...

Data Manipulation (SQL/Python)
0
0
5 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Aggregate video time and unique pins in Python

Part A (category by average time for videos): You receive a list of pin engagement rows and a category map. pins = [ {"pin_id": 10, "category_id": 1,...

Data Manipulation (SQL/Python)
1
0
8 people solved
Oct 13, 2025
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Pinterest
Medium
Data Scientist

Calculate 95% Bootstrap Confidence Interval for Order Values

Scenario An e-commerce firm wants a 95% confidence interval for the average order value but only has a single historical sample of order amounts. Ques...

Coding & Algorithms
27
0
45 people solved
Aug 4, 2025
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Pinterest
Medium
Data Scientist

Find available reservation time slots

Problem You are building an API to show which time slots are available for booking at a restaurant. You are given: - The restaurant’s opening hours (p...

Coding & Algorithms
12
0
101 people solved
Aug 2, 2025
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Pinterest
Medium
Data Scientist

Implement Binary Search for Policy Violation Logs

violations +--------+---------+---------------+ | pin_id | type | violation_date| +--------+---------+---------------+ | 0 | spam | 2022-01...

Data Manipulation (SQL/Python)
57
0
5 people solved
Jul 12, 2025
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Pinterest
Medium
Data Scientist

Implement DelayQueue with Idempotent Task Execution

Scenario Message broker offers DelayQueue where tasks execute at future timestamps, ensuring idempotency on duplicate IDs. Question Implement a delay ...

Coding & Algorithms
29
0
68 people solved
Jul 12, 2025
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Pinterest
Medium
Data Scientist

Implement LRUCache with O(1) Operations and Thread Safety

Scenario High-traffic API needs constant-time eviction cache. Question Implement an LRUCache supporting get(key) and put(key,val) in O( 1). Describe ...

Coding & Algorithms
16
0
62 people solved
Jul 12, 2025
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Pinterest
Medium
Data Scientist

Develop Auto-Complete System for Dish Suggestions

Scenario Search-as-you-type needs dish suggestions with popularity scores. Question Build an auto-complete system using the given (string, score) tupl...

Coding & Algorithms
5
0
25 people solved
Jul 12, 2025
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Pinterest
Medium
Data Scientist

Decode and Explain Ambiguity in Compression Strings

Scenario Compression library that encodes an array as count-value pairs where value is one digit but count may be many digits. Question Implement deco...

Coding & Algorithms
14
0
38 people solved
Jul 12, 2025

Frequently Asked Questions

How difficult are Pinterest interview questions for this 145-question set?
Pinterest interview difficulty varies by role and seniority. Across the 145 real questions in this set, expect medium-to-hard difficulty for software engineers with emphasis on clean algorithmic solutions and system tradeoffs, and moderate-to-hard for data scientists where product-focused experimentation, SQL, and causal reasoning are evaluated. Machine learning engineer rounds skew toward applied ML fundamentals and recommender/search design, while data analyst items are relatively straightforward metric calculations. Overall, interviews test both implementation fluency and product judgment — solving a problem correctly is necessary, but explaining assumptions, metrics, and tradeoffs is equally important.
What is the typical Pinterest interview process and where do these roles appear in the loop?
Pinterest interviews usually begin with a recruiter screen, followed by one or two technical screens tailored to the role, then a loop of 3–5 onsite or virtual interviews covering coding, system or ML design, and behavioral/manager rounds. Software engineer candidates see coding and system-design-focused rounds; data scientists face coding plus product-case and experimentation rounds; machine learning engineers combine coding with model design and recommender/search architecture; data analysts are asked metric and SQL problems. Expect the role to surface early in the loop during the technical screens so prepare role-specific artifacts and examples in advance.
How should I schedule preparation across the 145 real Pinterest interview questions — what timeline works best?
For 145 questions allocate a structured 6–8 week plan: weeks 1–2 reinforce fundamentals — arrays, strings, hashes, SQL joins/aggregates, and core ML statistics; weeks 3–5 work through the dataset: alternate role-specific blocks (coding for engineers, experiment and SQL cases for data scientists, model and recommender design for MLEs) and time-box solving full questions under interview conditions; final 1–2 weeks run timed mock interviews, system design walkthroughs, and behavioral STAR rehearsals. Review mistakes, write clean solutions, and practice explaining metrics and tradeoffs out loud before interviewing.
What are the key technical subtopics to prioritize from these Pinterest questions?
Prioritize the themes that appear repeatedly by role. For data scientists focus on experiment design and lift evaluation (carousel and billboard cases), weighted or random sampling implementations, SQL aggregation for top categories and engagement metrics, and handling survey biases. Software engineers should emphasize prefix/autocomplete patterns, pipeline and storage design, sparse-matrix algorithms, graph and grid search problems, and reliability for blob/event systems. Machine learning engineers need search/recommender architecture, model fundamentals (bagging, Naive Bayes), hyperparameter grid generation, and overfitting diagnostics. Data analyst items concentrate on retention and cancellation percent calculations.
What standout tips and common pitfalls should I watch for when prepping these Pinterest interview questions?
Lead with product context and metrics: state the business goal, choose evaluation metrics, and justify tradeoffs. Communicate assumptions, handle edge cases, and write tests or sample outputs for coding/SQL answers. For experiments, state randomization strategy, power implications, and bias controls. For ML, discuss features, regularization, and validation to avoid overfitting. Pitfalls include skipping requirement clarifications, ignoring NULLs or real data skew, overengineering a solution, and failing to link technical choices back to user or business impact. Practice concise storytelling for behavioral rounds and timed mock interviews for fluency.

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