# Software Engineer 2
**Role:** Software Engineer · **Level:** L5
**Company:** [Affirm](https://scaleengineer.com/companies/affirm)
**Difficulty:** Medium to Hard
**Salary:** US$130000 - US$160000
**Experience:** 3 - 5
**Timeline:** ~7 days
The Software Engineer 2 (L5) interview at Affirm is designed to assess a candidate's technical proficiency, problem-solving abilities, system design skills, and cultural fit. This role typically requires 3-5 years of relevant experience. The process involves multiple rounds, including technical interviews, a system design interview, and a behavioral/managerial interview.
Canonical: https://scaleengineer.com/interviews/affirm/l5-software-engineer
---
## Overall evaluation

- Technical Skills
- Behavioral and Cultural Fit

## Questions asked

- Given an array of integers, find the contiguous subarray with the largest sum.
- Design a system to shorten URLs.
- Describe a time you had to deal with a difficult stakeholder.
- How would you implement a cache for a web application?
- What are the differences between TCP and UDP?
- Tell me about a project you are particularly proud of.
- How do you handle production incidents?
- Design a notification system.
- Explain the concept of eventual consistency.
- What are your career goals?

## Preparation tips

### lists

- Review fundamental data structures and algorithms (arrays, linked lists, trees, graphs, hash maps, sorting, searching).
- Practice coding problems on platforms like LeetCode, HackerRank, or similar.
- Study system design principles (scalability, availability, consistency, databases, caching, load balancing, message queues).
- Prepare to discuss your past projects in detail, focusing on your contributions and technical challenges.
- Understand Affirm's business model, products, and values.
- Practice behavioral questions using the STAR method (Situation, Task, Action, Result).
- Prepare questions to ask the interviewer about the role, team, and company culture.

### studyPlan

- {"title":"Data Structures and Algorithms Fundamentals","longDescription":"Week 1-2: Focus on core data structures (arrays, linked lists, stacks, queues, trees, graphs, hash tables) and algorithms (sorting, searching, recursion, dynamic programming). Practice implementing these and solving related problems on platforms like LeetCode (Easy/Medium).","shortDescription":"Weeks 1-2: Data Structures & Algorithms (Easy/Medium)"}
- {"title":"System Design Principles","longDescription":"Week 3: Deep dive into system design concepts. Study topics like API design, database choices (SQL vs. NoSQL), caching strategies, load balancing, message queues, and distributed system patterns. Read relevant articles and case studies.","shortDescription":"Week 3: System Design Concepts"}
- {"title":"System Design Application","longDescription":"Week 4: Practice system design problems. Work through common scenarios like designing a URL shortener, a Twitter feed, or a rate limiter. Focus on trade-offs and justifying your design choices.","shortDescription":"Week 4: System Design Practice"}
- {"title":"Behavioral Interview Preparation","longDescription":"Week 5: Prepare for behavioral interviews. Reflect on your past experiences and prepare stories using the STAR method for common questions related to teamwork, leadership, conflict resolution, and handling failure.","shortDescription":"Week 5: Behavioral Interview Prep"}
- {"title":"Company and Role Alignment","longDescription":"Week 6: Review Affirm's business, products, and values. Research recent news and company initiatives. Prepare thoughtful questions to ask the interviewers.","shortDescription":"Week 6: Company Research & Questions"}

## Location differences

- {"location":"San Francisco, USA","differences":{"tips":["Be prepared to discuss specific examples from your experience that demonstrate problem-solving and collaboration.","Familiarize yourself with Affirm's business and how technology supports it.","Practice explaining complex technical concepts clearly and concisely.","Research common interview questions for L5 Software Engineers at similar tech companies."],"interviewFocus":["Emphasis on practical application of data structures and algorithms.","Deeper dive into distributed systems concepts relevant to Affirm's platform.","Understanding of cloud-native technologies (AWS, Kubernetes).","Cultural alignment with Affirm's values (e.g., customer obsession, bias for action)."],"commonQuestions":["Discuss a challenging technical problem you solved at your previous company.","How do you approach debugging a complex issue in a distributed system?","Describe a time you had to mentor a junior engineer.","What are your thoughts on microservices vs. monolith architectures in the context of e-commerce?","How do you ensure the scalability and reliability of your code?"]}}
- {"location":"Remote (Global)","differences":{"tips":["Prepare to draw system diagrams and explain your design choices thoroughly.","Highlight experience with internationalization and localization if applicable.","Showcase your ability to communicate technical ideas effectively across different teams and time zones.","Understand the challenges of operating at scale in different regulatory environments."],"interviewFocus":["Focus on system design and architectural patterns.","Understanding of scalability, performance, and reliability in a global context.","Experience with data processing and analytics pipelines.","Demonstrated ability to work effectively in a remote or hybrid team environment."],"commonQuestions":["Explain the trade-offs between different database technologies for a high-throughput application.","How would you design a rate-limiting system for an API?","Describe a situation where you disagreed with a technical decision and how you handled it.","What are the key considerations for building a fault-tolerant system?","How do you stay updated with new technologies and best practices?"]}}

## Round 1: Data Structures and Algorithms
**Type:** Technical Interview (Coding) · **Difficulty:** Medium · **Duration:** 45 min
Coding challenge focused on data structures and algorithms.
This round focuses on your fundamental programming skills. You will be asked to solve one or two coding problems, typically involving data structures and algorithms. The interviewer will assess your ability to understand the problem, devise a solution, write clean code, and explain your thought process. Expect to discuss time and space complexity and potential optimizations.
**Interviewers look for:** Strong problem-solving skills.; Proficiency in at least one programming language.; Ability to write clean and efficient code.; Understanding of time and space complexity.
**Evaluation criteria:** Correctness of the solution.; Efficiency of the algorithm (time and space complexity).; Code clarity and style.; Ability to explain the thought process.; Handling of edge cases.
**Common rejection reasons:** Inability to solve coding problems efficiently.; Poor code quality (not clean, readable, or maintainable).; Lack of understanding of fundamental data structures and algorithms.; Failure to consider edge cases or optimize solutions.
## Questions

- Given a binary tree, invert the tree.
- Find the kth largest element in an unsorted array.

## Preparation tips

- Practice coding problems on platforms like LeetCode, focusing on medium-difficulty questions.
- Be comfortable explaining your approach before you start coding.
- Write code that is readable and well-commented.
- Test your code with various inputs, including edge cases.

## Round 2: System Design
**Type:** System Design Interview · **Difficulty:** Hard · **Duration:** 60 min
Design a scalable system based on a given problem statement.
This round assesses your ability to design scalable and robust systems. You'll be given an open-ended problem (e.g., design a URL shortener, a social media feed) and expected to design a high-level architecture. This includes defining APIs, choosing databases, discussing caching strategies, load balancing, and addressing potential bottlenecks and failure scenarios.
**Interviewers look for:** Ability to design complex systems from scratch.; Understanding of trade-offs in system design.; Knowledge of distributed systems, databases, caching, and messaging.; Ability to communicate design ideas effectively.
**Evaluation criteria:** Scalability of the proposed design.; Reliability and fault tolerance.; Clarity and completeness of the design.; Justification of technology choices and trade-offs.; Ability to handle various constraints and requirements.; Understanding of distributed systems concepts.
**Common rejection reasons:** Inability to design a scalable and reliable system.; Lack of understanding of core system design concepts.; Poor justification of design choices and trade-offs.; Failure to consider aspects like availability, consistency, and performance.; Not asking clarifying questions.
## Questions

- Design a rate limiter for an API.
- Design a distributed cache system.

## Preparation tips

- Study common system design patterns and concepts.
- Practice designing various systems, focusing on trade-offs.
- Be prepared to draw diagrams and explain your design choices.
- Ask clarifying questions to understand the scope and constraints of the problem.

## Round 3: Behavioral and Managerial Fit
**Type:** Behavioral / Managerial Interview · **Difficulty:** Medium · **Duration:** 45 min
Assesses cultural fit, teamwork, and past experiences.
This round focuses on your behavioral and cultural fit. The interviewer will ask questions about your past experiences, how you handle different situations (e.g., conflict, failure, success), your motivations, and your career goals. Using the STAR method (Situation, Task, Action, Result) is highly recommended for answering these questions.
**Interviewers look for:** Cultural fit with Affirm.; Ability to work effectively in a team.; Demonstrated ownership and accountability.; Growth mindset and willingness to learn.; Good communication and interpersonal skills.
**Evaluation criteria:** Alignment with Affirm's core values.; Collaboration and teamwork skills.; Problem-solving approach in past experiences.; Leadership potential.; Communication clarity.; Motivation and career aspirations.
**Common rejection reasons:** Lack of alignment with company values.; Poor communication or interpersonal skills.; Inability to provide specific examples for behavioral questions.; Lack of enthusiasm or interest in the role/company.; Negative attitude or inability to handle feedback.
## Questions

- Tell me about a time you failed and what you learned from it.
- Describe a situation where you had to work with a difficult team member.

## Preparation tips

- Prepare specific examples using the STAR method for common behavioral questions.
- Research Affirm's company culture and values.
- Be ready to discuss your strengths and weaknesses.
- Show enthusiasm for the role and the company.