Scale Engineer

Software Engineer 1

Software EngineerL4Medium

The Software Engineer 1 (L4) interview at Affirm is designed to assess a candidate's foundational software engineering skills, problem-solving abilities, and cultural fit. It typically involves a mix of technical and behavioral assessments to ensure the candidate can contribute effectively to Affirm's engineering teams.

Rounds·3

Timeline·~10d

Experience·2 - 5 yrs

Comp band·US$110000 - US$140000

Interview time·135 min

Evaluation

What they measure.

  • Problem-solving approach
  • Coding proficiency (clean, efficient, well-structured code)
  • Understanding of data structures and algorithms
  • System design principles (for relevant roles/levels)
  • Communication skills
  • Collaboration and teamwork
  • Cultural alignment with Affirm's values (e.g., empathy, ownership, growth)

Preparation

How to prepare.

Tips

  1. Review fundamental data structures (arrays, linked lists, trees, graphs, hash maps) and algorithms (sorting, searching, dynamic programming, graph traversal).
  2. Practice coding problems on platforms like LeetCode, HackerRank, or Coderbyte, focusing on medium-difficulty problems.
  3. Brush up on core computer science concepts such as operating systems, databases, and networking.
  4. Prepare for behavioral questions using the STAR method (Situation, Task, Action, Result).
  5. Understand Affirm's business, products, and engineering culture.
  6. Prepare questions to ask the interviewer about the role, team, and company.

Study plan

Fig · Study plan — 04 phases

01 / 04
01

Phase 01 of 04

Data Structures & Complexity

Weeks 1-2: Data Structures (Arrays, Lists, Trees, Graphs, Hash Tables) & Complexity Analysis.

Weeks 1-2: Focus on Data Structures. Cover arrays, linked lists, stacks, queues, hash tables, trees (binary trees, BSTs, heaps), and graphs. Practice implementing these and solving problems related to them. Understand time and space complexity (Big O notation).

Questions

Commonly asked.

  • Write a function to reverse a linked list.
  • Given an array of integers, find the contiguous subarray with the largest sum.
  • Design a system to store and retrieve user profiles.
  • Explain the concept of RESTful APIs.
  • Tell me about a time you failed and what you learned from it.
  • How would you optimize a slow database query?
  • Describe your experience with version control systems like Git.

Locations

Regional differences.

Fig · Regions — 02 locations

01 / 02

Location

San Francisco, USA

Interview focus

Emphasis on practical coding skills and understanding of core CS concepts.Assessment of collaboration and communication skills in a team setting.

Common questions

  • How would you design a URL shortener?
  • Explain the difference between a process and a thread.
  • Describe a challenging technical problem you solved and how you approached it.
  • Tell me about a time you disagreed with a teammate and how you resolved it.

Tips

  • Be prepared to whiteboard solutions for common data structures and algorithms problems.
  • Practice explaining your thought process clearly and concisely.
  • Research Affirm's products and values to tailor your behavioral answers.

Rounds

Round-by-round.

Expand a step for evaluation criteria, sample questions, and prep notes.

Med

Technical (Coding) · 45 min · Software Engineer

This round typically involves a coding challenge, often presented as a problem to solve on a shared editor or whiteboard. The interviewer will assess your ability to translate a problem into code, your understanding of data structures and algorithms, and your approach to testing and debugging. Expect to discuss your solution and its time/space complexity.

What they look for

A structured approach to problem-solvingClean, efficient, and correct codeAbility to explain the solution and its trade-offsBasic understanding of CS fundamentals

Evaluation

  • Problem-solving approach
  • Coding proficiency
  • Understanding of data structures and algorithms
  • Communication clarity

Sample questions

  • Given a string, find the length of the longest substring without repeating characters.

    StringSliding WindowHash Map

  • Implement a function to check if a binary tree is a Binary Search Tree (BST).

    TreeRecursionBinary Search Tree

Prep for this round

  1. 01Practice coding problems under timed conditions.
  2. 02Focus on writing clean, readable, and well-commented code.
  3. 03Be prepared to explain your code line by line.
  4. 04Think about edge cases and how to handle them.

Common rejection reasons

  • ×Inability to articulate thought process
  • ×Poor coding practices (unreadable, inefficient code)
  • ×Fundamental misunderstanding of data structures or algorithms
  • ×Lack of enthusiasm or engagement

DSA

Coding questions at Affirm.

Frequently reported on Affirm loops

View all at Affirm

Other guides

More at Affirm.