Coding fluency
Implement an LRU cache. Explain your data structures, test capacity one, and walk through an eviction.
What a strong answer demonstrates
Correctness, edge cases, and time / space complexity.
Prepare for Square with a focused mix of coding, design, and communication. Start with your job description and confirm the interview loop with your recruiter.
10 Question notes
6 Practice picks
5 Levels mapped
01 / MAKE YOUR NEXT SESSION COUNT
Your preparation, made concrete.
System design
Design a notification service. Clarify delivery guarantees, model the data, then handle retries and duplicate events.
What a strong answer demonstrates
Clear requirements, a working baseline, and explicit trade-offs.
Behavioral storytelling
Describe a technical decision you changed after receiving feedback. Explain your contribution and the outcome.
What a strong answer demonstrates
Specific actions, honest reflection, and measurable impact.
BEFORE YOU PRACTICE
Ask your recruiter.
Get the details that a generic company guide cannot know.
- Which team and level is this opening for, and what does success look like?
- What rounds, durations, and evaluation criteria should I prepare for?
- Which languages, tools, and AI assistance are permitted?
- Will design focus on frontend, backend, infrastructure, or another specialty?
- Are there accommodations or preparation materials I should request?
Square practice problems
Company-linked challenges and related lessons from our library. Not a prediction of your interview.
Challenge
Difficulty 4/10
Product Except Self
Challenge
Difficulty 7/10
Design A Least Recently Used (LRU) Cache
Challenge
Difficulty 7/10
Matrix Operations
Challenge
Difficulty 6/10
Two Stack Queue
Challenge
Difficulty 5/10
Find Shortest Palindrome Possible
Challenge
Difficulty 5/10
Sorted Two Sum
Questions candidates have reported
Aggregated from candidate submissions and public sources.
Q1
Matrix Operations: Input: two numbers, N and M, which define an NxM grid
start at top left corner of grid (1,1):
- step forward
- turn right
- if space in front of you is out of board or you already walked on it, turn right
Keep going until you can’t walk anymore. The output is number of steps you take before stopping.
Q2
Validate Symbols: Generate all combinations of M given N different items then find the all the valid pairs in a subset of the generated set.
Q3
Design Least Recently Used Cache: Implement an LRU cache.
Q4
Implement a Hash Map: Write a wrapper around the python dictionary data structure and implement commonly used methods for it. Also write unit tests for each of those methods.
Q5
Input: coefficients line (a’s), lines of values from transactions (x’s)
y = a0 + a1*x1 + a2*x2 + ... + an*xn
y <= 0 not fraud, y > 0 suspect fraud
output fraud/not fraud for each line of n lines.
Q6
Describe a oo design for a deck of cards.
Q7
Given an architecture, describe possible approaches to minimizing latency and downtime.
Q8
How would you code a program that gives you the day of the week given a date?
Q9
In the x/y plane, create a function that stacks blocks on top of each other like they do in tetris.
Q10
Design a calendar api.
Engineering levels & compensation
Historical figures from existing records; date and location may be unspecified. Verify current ranges on Levels.fyi.
Level 1
Level 3
$189,400
$131,000 base · $52,400 stock · $6,000 bonus
Level 2
Level 4
Not Available
Level 3
Level 5
$288,100
$160,200 base · $127,000 stock · $900 bonus
Level 4
Level 6
$434,250
$193,000 base · $233,750 stock · $7,500 bonus
Level 5
Level 7
Not Available
What people at Square say
Reviews originally posted on Glassdoor.
If you are mission driven, then you would enjoy this company and it's mission of Economic Empowerment. Lots of interesting business problems to solve. These problems often translate into complex engineering challenges. Square also has scale both in terms of product and org. Most recently a lot of groups started the long journey of cloud migration. Overall technical direction of the company is often missing and it's left to teams to get aligned. While this meritocratic approach can lead to best team's solution wins situations, this is not always the case. Technical decision making is often slow as a result of this approach.
In software engineering, you are exposed to all kinds of interesting problems in the financial space. Engineering talent was a positive surprise. Company grew from 2000 to almost 4000 relatively quickly. Career advancement can depend on department and manager, although it's a very typical problem at most places I have been working at. Being on-call is expected. The on-call experience is also very team dependent.
We’re empowering the small business owners and entrepreneurs of the world Square has huge growth potential Growth potential means growth opportunities for all of us as employees Square is very efficiently managed without all of the waste of many SF companies. This business knows how to grow All of my coworkers are insanely smart. Very few. The 401k match was capped at 1500 in 2017 but its doubling for 2018. This is still a bit low compared to some other companies but not too bad.
As a developer specifically, great engineering culture, they actually care about things like testing their code that many startups only give lip service to. Still has a startup-like atmosphere for a pretty old company. Some nice fringe benefits, health/dental/vision 100% lots of cheap-to-free food. Low salaries for a public company, equity compensation for me was equal to about 1 year salary but vesting over 4 years, even including the 25% premium it’s still low for the SF bay area. Required engineers to be on-call, at least on my team, but did not properly compensate. I have never worked anywhere that required engineers to be on-call unless it was shortly after a launch maybe they would be expected to fix their code if it failed catastrophically but not like this.
Management is really supportive and puts a huge emphasis on how they are there to help you. In addition, my co-workers are all very receptive to questions and are always willing to help. I also really appreciate the culinary team here - the food here is out of this world! The company is really aware about diversity and social issues. The art and design team is really strong here and I love working with beautiful products! It's also really exciting to see the company grow at such a fast rate!Keep it up! I really like how things are right now and I'm glad the company is transparent in everything that it does.
Inside the workplace
About Square
A day at Square