Square

Large Enterprises

Square, part of Block, Inc., is a financial services and digital payments company that provides point-of-sale hardware, software, and payment processing tools for businesses. It is known for enabling small and medium-sized merchants to accept card payments and manage their operations through an integrated ecosystem.

6 interview notes · updated Jul 2026

Square·Software Engineer·Technical Phone Screen

Jun 2026

Square SWE interview that was basically one long graph problem broken into three escalating parts. The setup was clean but by part three I was definitely scrambling to keep the BFS logic straight while also talking through it out loud.

Design a class to record transactions between pairs of customers and answer whether two customers have ever been part of the same connected component in the transaction graph.
Extend your solution to return everyone reachable from a given customer through any chain of transactions, excluding the customer themselves.
Further extend the network query to accept a degree limit, returning only customers within at most N hops from the given person.

“The union-find angle came to me pretty fast, which was good.”

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Square·Software Engineer·Technical Phone Screen

Jun 2026

Square coding interview, one question about transaction graph lookups. Pretty focused and not too long, but the problem had some interesting design decisions hiding under the surface.

Design a class that processes a stream of transactions between customers and supports a query to check whether two specific customers have ever directly transacted with each other.

“My first instinct was a hashmap where each customer maps to a set of everyone they've transacted with.”

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Square·Software Engineer·Onsite - Product Sense / Strategy

Jun 2026

PMM interview at Square, one question about launching a new feature for their salon product. Pretty open-ended and I wasn't totally sure how deep they wanted me to go on execution vs. strategy.

You're a product marketing manager. Walk me through how you'd launch a new waitlist appointment feature for a salon business.

“I started with audience segmentation and kind of rambled for a bit before pulling it together around positioning and channel strategy.”

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Square·Software Engineer·Technical Phone Screen

Jun 2026

Square coding interview, one question about extending a graph traversal method. Pretty focused session, no fluff.

You have a method that finds all customers connected in a network. Modify it to accept a depth parameter n, and return only customers within n degrees of separation from a given starting customer using BFS.

“BFS with a depth limit is something I'd done before but I fumbled the layer-tracking part initially.”

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Square·Product Manager·Onsite - Product Sense / Strategy

May 2026

PM interview at Square with a strategy question about a staff training product they'd recently shipped. One question, pretty open-ended, felt like they wanted to see how you think about growth levers rather than hear a perfect answer.

Square recently launched a product that helps sellers train their staff. How would you grow its revenue 5x over the next year?

“I went straight to acquisition and kind of ignored monetization depth, which in hindsight was a mistake.”

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Square·Software Engineer·Technical Phone Screen

May 2026

Square coding interview, graph traversal problem built on top of a transaction tracking system they had you extend. Pretty clean problem once you saw it for what it was.

Given an existing customer transaction tracker, implement a method that takes a customer and returns all customers reachable through any chain of transactions, essentially finding the connected component for that customer in the transaction graph.

“Took me a second to see it as a graph problem.”

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