Preparing for an interview at Affirm requires a balanced approach that addresses both technical precision and behavioral alignment. You should focus on demonstrating not just your ability to write code, but how you think about software as a craft and how you collaborate with others.

Technical Execution and Speed – At Affirm, coding rounds are conducted in live, browser-based IDEs where your code must compile and run against real test cases. You are evaluated on your ability to quickly translate an algorithmic approach into clean, modular, and bug-free code.

System Architecture and API Design – You must demonstrate a strong grasp of distributed systems, API design, and data modeling. Interviewers look for candidates who can articulate the trade-offs between different database technologies, caching strategies, and system boundaries.

Behavioral Alignment and DEI – Affirm places a massive emphasis on its core values, particularly Diversity, Equity, and Inclusion (DEI). Be prepared to discuss your personal experiences with fostering inclusive environments and how you integrate these principles into your daily engineering practices.

Ownership and Collaboration – You will be evaluated on how you take ownership of projects, handle technical disagreements, and collaborate with cross-functional partners. Use the STAR method (Situation, Task, Action, Result) to structure your behavioral responses clearly.

The interview loop at Affirm is comprehensive and designed to evaluate your technical competency, system design instincts, and cultural fit. The process is highly structured, moving from initial conversational screens to deep-dive technical assessments.

The loop typically begins with a recruiter pre-screen, followed by an initial technical screen which may consist of an online assessment or a live coding interview. If you pass the initial stage, you will proceed to a hiring manager screen where the focus shifts toward your background, technical interests, and high-level architecture experience. The final stage is a virtual onsite consisting of multiple technical and behavioral rounds.

Affirm's interviewing philosophy emphasizes practical, real-world engineering skills over abstract brainteasers. The coding challenges often mirror actual scenarios faced by the engineering teams, such as transaction processing or game-like simulations.

The visual timeline above outlines the typical progression of a candidate through the Affirm hiring pipeline. You should use this sequence to pace your preparation, focusing first on core algorithms and then transitioning to system design and behavioral scenarios as you approach the final rounds. Note that while some teams may offer a take-home assessment in place of the initial technical screen, the virtual onsite will always feature live, interactive coding.

To excel in the Affirm interview loop, you must understand the specific technical and behavioral dimensions upon which you will be graded.

Practical Coding and Implementation

The practical coding rounds at Affirm are designed to evaluate your hands-on programming ability. Unlike companies that allow pseudo-code or whiteboard sketches, Affirm requires you to write fully functional, compilable code that passes concrete test suites within a limited timeframe.

Be ready to go over:

• Object-Oriented Design – Organizing your code into logical classes, interfaces, and modules. For example, when implementing a card game, you should cleanly separate the deck, player, and game engine logic.
• Data Structure Selection – Utilizing the most effective built-in data structures (such as HashMaps, Queues, and Sets) to optimize your code's time and space complexity.
• String and Data Manipulation – Parsing, filtering, and transforming raw input data efficiently, which is a common requirement in fintech applications.
• Advanced concepts (less common):
  • Custom memory-efficient data structures.
  • State machine implementations for complex business rules.

Example questions or scenarios:

• "Implement a card game with $N$ players and $M$ cards, ensuring your classes are modular enough to support future extensions like custom card values or dynamic player counts."
• "Write an algorithm to parse a series of raw ledger entries, validate their consistency, and return a structured summary of account balances."

System and Low-Level Design

System design interviews at Affirm focus heavily on your ability to architect reliable, secure, and scalable services. Given the financial nature of the product, topics like data consistency, idempotency, and auditability are of paramount importance.

Be ready to go over:

• API Design – Defining clear, RESTful, or gRPC endpoints, including request and response payloads, status codes, and error handling mechanisms.
• Data Modeling – Designing relational and non-relational database schemas, understanding transaction isolation levels, and ensuring data integrity.
• Scalability and Reliability – Mitigating single points of failure, implementing caching layers, and managing high-throughput message queues.
• Advanced concepts (less common):
  • Event sourcing and CQRS patterns for financial ledgers.
  • Distributed transaction management and saga patterns.

Example questions or scenarios:

• "Design the backend architecture for a virtual credit card issuing service, detailing the API contract, database schema, and how you prevent double-spending."
• "Architect a high-volume merchant analytics platform that aggregates transaction data in real-time while maintaining strict read-write isolation."

Behavioral and Core Values Alignment

The behavioral interviews at Affirm are just as critical as the technical assessments. The company looks for engineers who are not only technically brilliant but also empathetic, collaborative, and deeply aligned with the company's mission.

Be ready to go over:

• Diversity, Equity, and Inclusion (DEI) – Sharing your concrete thoughts and past actions regarding workplace equity and how you contribute to an inclusive engineering culture.
• Ownership and Accountability – Demonstrating how you take responsibility for your code, learn from production failures, and drive projects to completion.
• Constructive Collaboration – Navigating healthy technical disagreements, mentoring junior engineers, and communicating effectively with non-technical stakeholders.

Example questions or scenarios:

• "Tell me about a time when you noticed an inequitable process or dynamic on your team, and what actions you took to address it."
• "Describe a past project that failed to meet its deadline or technical goals. What went wrong, and how did you manage the aftermath?"