Pinterest Interview Questions — Page 11

Pinterest·Software Engineer·Technical Phone Screen

May 2026

Pinterest iOS system design question, basically one big open-ended build prompt. No behavioral stuff, just deep on mobile architecture for a continuous animation feature.

Design and build an iOS app where holding a button continuously fires emoji projectiles that animate toward the top of the screen. Walk through your animation approach, how you'd schedule the continuous firing, handle off-screen cleanup, manage performance under many concurrent animations, and structure the code for testability.

“This one sprawled fast.”

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Pinterest·Machine Learning Engineer·Technical Phone Screen

May 2026

Pinterest ML Engineer screen that was basically a 'can you do arithmetic with neural nets' exercise. One question, very hands-on, felt more like a math exam than a real interview.

Given a small neural network with specific weights, biases, and an input vector, compute the forward pass by hand. Show all intermediate pre-activations and post-activations at each layer using the sigmoid function.

“I spent the first few minutes just confirming the architecture because I've been burned before assuming things.”

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Pinterest·Product Manager·Onsite - Product Sense / Strategy

May 2026

Interviewed for a PM role at Pinterest and got a strategy question about a well-known acquisition. Not much else to report.

Why did Google acquire YouTube?

“Tried to work through it as a product strategy case: distribution, video infrastructure, ad inventory.”

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Pinterest·Machine Learning Engineer·Technical Phone Screen

May 2026

Pinterest ML engineer interview with a system design problem around hierarchical access control. The problem itself was clean but the follow-up complexity snuck up on me.

Design a class that manages advertiser permissions on a group hierarchy tree, supporting grant, revoke, and check access operations where permissions propagate from parent nodes to all descendants.

“The basic structure came together fine, grant and revoke are just set operations on a per-advertiser collection of group IDs, and check_access walks up the tree comparing ancestors.”

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Pinterest·Product Manager·Onsite - Product Sense / Strategy

May 2026

Pinterest PM interview with a product sense question about Google Search. Single question, focused on redesigning a familiar product's user journey, which sounds easy until you realize how much you take the search landing page for granted.

Given that Google Search has essentially stayed the same as a simple text input without much innovation, how would you improve the user journey starting from the landing page?

“My first instinct was to go broad and list features, which was probably the wrong move.”

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Pinterest·Data Scientist·Technical Phone Screen

May 2026

Pinterest data scientist interview that went pretty deep into algorithmic territory. The main problem was a calendar booking system and it kept branching into follow-ups I wasn't fully ready for.

Design and implement a booking system similar to LeetCode 732 (My Calendar III): a class with a book(start, end) method using half-open intervals that returns the maximum number of concurrent bookings after each call. Target O(log n) amortized time and O(n) space for up to 100,000 operations.
How do you precisely handle duplicate and nested intervals in this booking system? State your boundary convention explicitly and write unit tests that would catch off-by-one bugs, for example book(10,20), book(20,30), and book(15,25).
Add a cancel(start, end) method that removes a previously booked interval and keeps the returned maximum-k accurate for all future calls. Also add a query(t) method that returns the number of active bookings at a specific time t in O(log n).
Analyze the worst-case time and space complexity of your solution. How does your data structure avoid O(n) per operation under adversarial input like many overlapping single-point intervals? What would you change if recursion depth or memory fragmentation became a real constraint?

“I went with the sweep-line difference map approach because I've used ordered maps before and felt more confident explaining the correctness argument.”

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Pinterest·Software Engineer·Technical Phone Screen

May 2026

Interviewed for a security engineer role at Pinterest, got a networking fundamentals question that I thought I'd nailed but kept second-guessing myself on the mitigation side.

What is ARP poisoning and how would you mitigate it?

“Explained the attack fine, ARP has no authentication so an attacker can broadcast fake MAC-to-IP mappings and redirect traffic.”

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Pinterest·Software Engineer·Technical Phone Screen

May 2026

Pinterest SWE interview with a meaty data structures question that had a lot more surface area than it looked at first glance. The problem sounds like a simple equality check until you realize sets can nest arbitrarily and order doesn't matter at any level.

Write a function to check if two arbitrarily nested sets are equal, where sets are represented as arrays (possibly containing integers or other nested arrays), order doesn't matter, and nesting can go as deep as needed. You also need to pick appropriate data structures, analyze complexity, write unit tests for given cases, and discuss trade-offs between canonicalization, hashing, and recursive approaches.

“I started with the canonicalization idea, basically sort everything recursively into a canonical form and then compare, which works but I fumbled explaining why you need a stable sort order for the nested sets specifically.”

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Pinterest·Data Scientist·Technical Phone Screen

May 2026

Pinterest DS interview with four back-to-back technical problems, two SQL and two Python/pandas. The questions were all grounded in Pinterest's actual product data model which was a nice touch, but the definitions were dense and easy to misread under pressure.

Write a SQL query that computes click-through rate broken down by pin format and event date, but only for users who are considered 'new' at the time of the event and are located in the US.
Write a SQL query to find what percentage of users saw at least one 'fresh' pin during a reporting window, where a fresh pin is defined as one that received at least 2 total impressions within 7 days of its creation.
Given a dictionary mapping board IDs to lists of pins, write a Python function that takes a target pin and returns all other pins ranked by how many boards they share with that pin. Support an optional parameter to limit results to the top N.
Using a pandas DataFrame of user engagement data, find the category with the highest average time spent among video pins only. The category name comes from an external mapping dict, and missing or null category IDs should be labeled 'unknown'. Also explain how you'd handle ties.

“The 'new user' definition is what gets you.”

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Pinterest·Software Engineer·Onsite - System Design / Architecture

May 2026

Pinterest system design round focused entirely on building an ads event reporting pipeline, end to end. Pretty deep cut for a single question, they clearly wanted to see how far you could go before running out of ideas.

Design an ads event reporting system that ingests user behavior events like impressions, clicks, and conversions, aggregates them, and breaks down those aggregates by user segments such as cohort, geography, and demographic. Walk through the full pipeline including ingestion, real-time vs batch processing, schema design, dimensional aggregation strategies, late-arriving events, deduplication, query patterns from a reporting dashboard, and storage choices.

“This one runs long.”

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