Preparing for the Software Engineer interview at AvidXchange requires a strategic approach. The evaluation process is designed to test both your foundational computer science knowledge and your practical, on-the-job engineering skills.

To succeed, you must demonstrate proficiency across the following key evaluation criteria:

• Algorithmic Problem Solving – You must be able to write clean, optimized code under time constraints. Interviewers evaluate your ability to identify the right data structures and algorithms, particularly in high-pressure, standardized testing environments.
• System and API Design – AvidXchange relies heavily on interconnected services. You will be assessed on how you architect solutions, design clean APIs, and handle ambiguous scenarios by asking the right clarifying questions.
• Domain-Specific Technical Depth – Your practical knowledge of core technologies is heavily scrutinized. Interviewers look for deep understanding of SQL optimization, object-oriented programming (OOP) principles, JavaScript asynchronous behavior, and .NET fundamentals.
• Operational Excellence and DevOps – Beyond writing code, you are evaluated on your understanding of how software is deployed, monitored, and maintained. Demonstrating knowledge of DevOps principles shows you understand the full software lifecycle.
• Culture Fit and Adaptability – Interviewers want to see how you handle feedback, communicate your thought process, and align with the mission of AvidXchange. Your ability to remain calm and structured, even when faced with poorly defined problems, is critical.

The interview process for a Software Engineer at AvidXchange is structured to efficiently filter candidates through a blend of internal behavioral screening and standardized, third-party technical assessments. You will typically begin with an initial phone screen with an internal recruiter. This conversation is focused on your background, your interest in AvidXchange, and high-level technical alignment. While mostly behavioral, be prepared for recruiters to ask basic technical trivia and take exact notes on your answers.

Following the initial screen, the technical heavy lifting begins with an outsourced technical interview conducted by Karat. This is a highly structured, one-hour session split between scenario-based API design questions and Leetcode-style coding challenges. Because this round is conducted by a third party, it can feel scripted and impersonal. Your goal here is to play by the rules of the standardized test: communicate clearly, ask clarifying questions, and write functional code swiftly.

If you pass the Karat screen, you will move to the final rounds, which consist of technical and behavioral interviews with AvidXchange engineers and engineering managers. These sessions are much more conversational and dive deep into your resume, your understanding of core technologies like SQL and .NET, and your cultural fit within the team.

This visual timeline outlines the typical progression from the initial recruiter screen to the final panel interviews. Use this to pace your preparation, focusing heavily on standard Data Structures and Algorithms (DSA) for the middle stage, and pivoting to deep, domain-specific trivia and system architecture for the final rounds. Note that timelines can occasionally stretch, so patience and proactive follow-ups are beneficial.

To excel in the AvidXchange interview process, you must be prepared to navigate distinct technical and behavioral evaluation areas. The process is bifurcated between standardized algorithmic testing and practical, domain-specific engineering discussions.

Data Structures and Algorithms (The Karat Interview)

The most critical hurdle for many candidates is the outsourced Karat interview. This area tests your raw coding speed, accuracy, and foundational computer science knowledge. Strong performance means solving at least two, ideally three, problems within a strict 45-minute window.

Be ready to go over:

• Graph Traversal – Deep understanding of Depth-First Search (DFS) and Breadth-First Search (BFS) is frequently tested.
• String and Array Manipulation – Core algorithmic patterns like sliding window or two-pointer techniques.
• Time and Space Complexity – You must be able to articulate the Big O notation for every solution you write.
• Advanced concepts (less common) – Dynamic programming or complex tree balancing, though these appear less frequently than standard graph problems.

Example questions or scenarios:

• "Given a grid representing a map, use DFS to find the number of distinct islands."
• "Write a function to determine if a directed graph contains a cycle."
• "Implement an algorithm to traverse a nested data structure and return a flattened array."

System and API Design

During the first 15 minutes of the Karat interview, and later in discussions with AvidXchange engineers, you will be evaluated on your system design intuition. This area tests how you structure data and endpoints for scalability and usability. Strong candidates do not just answer the prompt; they clarify the context before designing.

Be ready to go over:

• RESTful API Design – Best practices for routing, HTTP methods, and status codes.
• Data Modeling – How to structure database tables to support the proposed API.
• Handling Ambiguity – Navigating poorly phrased or context-lacking scenarios by asking targeted questions.
• Advanced concepts (less common) – Microservices communication, rate limiting, and caching strategies.

Example questions or scenarios:

• "Given a scenario where users need to upload and process large invoices, how would you design the API endpoints?"
• "Design a schema and API for a system that tracks user permissions across multiple organizations."
• "How would you handle a scenario where an API request fails halfway through a database transaction?"

Core Technologies: SQL, JavaScript, and .NET

Once you reach the internal AvidXchange interviews, the focus shifts dramatically to the practical technologies used on the job. Interviewers want to ensure you can contribute to their specific stack immediately. Strong performance here requires moving beyond surface-level knowledge and demonstrating a deep understanding of how these languages operate under the hood.

Be ready to go over:

• Advanced SQL – Deep knowledge of indexing, query optimization, and complex joins. You will be asked to write queries under specific constraints.
• JavaScript Fundamentals – Deep dive into asynchronous programming, Promises, and the event loop.
• OOP and .NET – Core object-oriented principles (Encapsulation, Inheritance, Polymorphism, Abstraction) and .NET framework fundamentals.
• Advanced concepts (less common) – CI/CD pipelines, containerization, and specific DevOps practices.

Example questions or scenarios:

• "Write a SQL query to find the second highest salary in a department, but you are absolutely not allowed to use any aggregate functions (like MAX or COUNT)."
• "Explain how Promises work in JavaScript and how you would handle multiple asynchronous API calls."
• "Discuss how you apply SOLID principles in a .NET application to ensure maintainability."