The Top American Express Software Engineer Interview Questions and How to Prepare

It can be both exciting and nerve-wracking to interview for a software engineering job at American Express. American Express, a top financial services company, is looking for strong technical candidates who can write good code and figure out hard problems.

I recently went through the American Express software engineering interview process and learned there are some common questions asked across multiple levels – from new grad software engineers to senior software engineers. Knowing what to expect can help you feel more confident and ace the coding, system design, and behavioral questions.

In this article, I’ll share details on some of the most frequent American Express software engineer interview questions and my tips on how to prepare

Overview of the American Express Software Engineering Interview Process

Even though each candidate’s interview may be a little different, American Express software engineering interviews usually go like this:

• 1 phone screen focusing on coding/algorithms
• 2-4 technical/coding rounds via video conference
• 1 system design round
• 1-2 behavioral/culture fit rounds

The coding rounds involve both algorithm questions as well as problems that resemble real-world software design and debugging. I’ll cover some examples of these later in the article.

The system design round assesses your skills in designing large scale systems and your knowledge of web/distributed architectures. This is an important part of the process for senior software engineering roles.

Finally, the behavioral interviews evaluate your communication skills, leadership abilities, and culture fit. American Express looks for engineers who are passionate, creative problem solvers and strong team players.

Common American Express Algorithm Interview Questions

Algorithms questions make up a major component of American Express’ software engineering interviews across both new grad and experienced roles

Here are some of the algorithm topics I encountered and recommend preparing for

• Arrays/Strings: A classic topic. Expect questions like checking if a string has unique characters, manipulating 2D arrays, and string manipulation.
• Linked Lists: Know how to traverse, insert, delete, reverse, and merge linked lists. Be able to implement basic operations.
• Trees: Study up on binary trees, binary search trees, tree traversal algorithms, etc. Understand how to construct, search, insert, delete, and balance trees.
• Graphs: Review graph representations, graph traversal algorithms like breadth-first search and depth-first search, shortest path algorithms, and common graph problems.
• Recursion: Get very comfortable with recursive solutions for trees, arrays, linked lists, etc. Know when recursion is appropriate.
• Dynamic Programming: Review tabulation and memoization approaches for Fibonacci, coin change, knapsack, etc.
• Sorting: Know how to implement bubble, merge, quick sorts and understand complexity.

For each topic, I’d recommend being able to code up solutions from scratch and analyze time/space complexity. LeetCode is great practice.

American Express Coding Interview Questions and Tips

In addition to algorithms, the American Express coding rounds contain more practical programming problems similar to what you might encounter on the job.

Here are some examples along with tips for tackling them:

Debugging

You may be given buggy code and asked to debug it. For example, identify the issue in code for performing a binary search on a sorted array.

• Take methodical approach: walk through example input, inspect edge cases, add print statements
• Explain thought process clearly to interviewer

Building Features/Apps

You could be asked to build parts of a real app like an e-commerce site’s shopping cart or rating system.

• Clarify requirements upfront
• Consider clean code principles like modularity, reusability, readability
• Discuss tradeoffs of different approaches

Refactoring

The interviewer may present you with working but messy code and ask how you would refactor it.

• Identify pain points: duplicated logic, poor naming, unnecessary complexity
• Apply OOP principles: encapsulate logic into classes/methods, separate concerns
• Communicate benefits of proposed changes

The key is to show strong programming fundamentals, communication skills, and ability to methodically solve problems.

Mastering the American Express System Design Interview

The system design interview is critical for experienced software engineering candidates to showcase their technical architecture skills. You’ll be asked to design a large scale system like Amazon, Uber, etc.

Follow these tips to stand out:

• Ask clarifying questions upfront to define scope and constraints
• Sketch high-level design and components. Explain choices.
• Discuss scalability and reliability considerations
• Analyze tradeoffs of different solutions
• Estimate capacity needs based on scale, traffic
• Consider future improvements like caching, load balancing

Demonstrate your breadth of knowledge and use of design principles over trying to get to a perfect solution.

Sample American Express Behavioral Interview Questions

American Express wants engineers who fit their collaborative, innovative culture. Expect questions like:

• Tell me about a time you faced a difficult obstacle on a project. How did you overcome it?
• When working on a team project, how do you ensure collaboration across members?
• Describe a time you made a mistake at work. How did you handle it?
• Why do you want to work at American Express specifically?

Highlight your problem-solving skills, communication abilities, and passion for the company. Use concrete examples versus general claims about your strengths.

How to Prepare for the American Express Software Engineering Interview

Here are my top tips for preparing:

• Thoroughly study data structures and algorithms. Master trees, graphs, recursion, DP, etc.
• Practice leetcode-style coding problems across multiple topics
• Strengthen object-oriented design skills using examples like online retail systems, social networks
• Refresh computer architecture knowledge like scaling, caching, microservices, etc.
• Research American Express products/tech stack to show motivation
• Practice communicating your approach clearly and calmly
• Get a good night’s rest! Eat a nutritious meal before the interviews