# Software Engineer III
**Role:** Software Engineer · **Level:** IC3
**Company:** [Reddit](https://scaleengineer.com/companies/reddit)
**Difficulty:** Medium to Hard
**Salary:** US$140000 - US$180000
**Experience:** 4 - 7
**Timeline:** ~14 days
This interview process is designed to assess candidates for the Software Engineer III (IC3) role at Reddit. It evaluates technical proficiency, problem-solving skills, system design capabilities, and cultural fit within the company.
Canonical: https://scaleengineer.com/interviews/reddit/ic3-software-engineer
---
## Overall evaluation

- Technical Skills
- Communication & Collaboration
- Cultural Fit & Potential

## Questions asked

- Design a system to handle Reddit's feed.
- How would you implement a real-time commenting system?
- Given a large dataset of user activity, how would you identify trending topics?
- Describe a challenging technical problem you solved.
- How do you ensure the scalability and reliability of your code?
- What are your thoughts on the trade-offs between different database technologies?
- Tell me about a time you mentored a junior engineer.
- How do you approach code reviews?
- What are your favorite programming languages and why?
- How would you optimize the performance of a slow API endpoint?

## 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 for scalable applications (databases, caching, load balancing, message queues, microservices).
- Understand common software engineering concepts like OOP, design patterns, testing, and debugging.
- Research Reddit's products, values, and recent news.
- Prepare behavioral questions using the STAR method (Situation, Task, Action, Result).
- Practice explaining your thought process clearly and concisely.
- Prepare questions to ask the interviewer about the role, team, and company culture.

### studyPlan

- {"title":"Data Structures and Algorithms","longDescription":"Weeks 1-2: Focus on core data structures (arrays, linked lists, stacks, queues, hash tables) and algorithms (sorting, searching, recursion, dynamic programming). Practice medium-difficulty problems on LeetCode.","shortDescription":"Weeks 1-2: Data Structures & Algorithms Fundamentals. Practice medium LeetCode."}
- {"title":"Advanced Data Structures and Algorithms","longDescription":"Weeks 3-4: Deep dive into trees (binary trees, BSTs, tries) and graphs (traversals, shortest path). Explore more complex algorithm patterns like greedy algorithms and backtracking. Continue practicing coding problems.","shortDescription":"Weeks 3-4: Advanced DS&A (Trees, Graphs). Practice complex LeetCode."}
- {"title":"System Design Fundamentals","longDescription":"Weeks 5-6: Begin system design preparation. Study concepts like scalability, availability, databases (SQL vs. NoSQL), caching strategies, load balancing, and message queues. Read system design case studies.","shortDescription":"Weeks 5-6: System Design Fundamentals. Study scalability, databases, caching."}
- {"title":"Advanced System Design","longDescription":"Weeks 7-8: Focus on advanced system design topics such as microservices architecture, API design, distributed systems, and consensus algorithms. Practice designing systems for common tech company problems.","shortDescription":"Weeks 7-8: Advanced System Design. Practice designing complex systems."}
- {"title":"Behavioral Preparation","longDescription":"Week 9: Prepare for behavioral and situational questions. Review your resume and identify key projects and experiences. Practice answering questions using the STAR method, focusing on leadership, teamwork, and problem-solving.","shortDescription":"Week 9: Behavioral Questions. Prepare STAR method answers."}
- {"title":"Mock Interviews","longDescription":"Week 10: Mock interviews. Conduct mock interviews with peers or mentors to simulate the actual interview environment. Get feedback on your technical explanations, problem-solving approach, and communication.","shortDescription":"Week 10: Mock Interviews. Simulate interview conditions."}

## Location differences

- {"location":"San Francisco, USA","differences":{"tips":["Familiarize yourself with Reddit's architecture and common technologies used.","Prepare examples of leading projects and mentoring junior engineers.","Be ready to discuss your experience with A/B testing and feature rollouts.","Highlight any experience with internationalization or localization if applicable to the role."],"interviewFocus":["System design for large-scale social platforms.","Understanding of distributed systems and scalability.","Experience with real-time data processing.","Collaboration and communication skills in a remote or hybrid environment."],"commonQuestions":["How would you design a URL shortener for Reddit?","Discuss a time you had to deal with a difficult stakeholder.","What are the trade-offs between SQL and NoSQL databases for a social media platform?","Describe a complex bug you encountered and how you debugged it."]}}
- {"location":"Dublin, Ireland","differences":{"tips":["Research Reddit's engineering blog and recent product launches.","Prepare to discuss your contributions to open-source projects if any.","Emphasize your ability to write clean, maintainable, and well-tested code.","Be ready to discuss your understanding of CI/CD pipelines."],"interviewFocus":["Scalability and performance optimization for high-traffic applications.","Experience with cloud infrastructure (AWS, GCP).","Problem-solving in a fast-paced, agile environment.","Ability to work independently and take ownership."],"commonQuestions":["How would you design a notification system for Reddit?","Tell me about a time you disagreed with a technical decision and how you handled it.","What are the challenges of scaling a social feed algorithm?","Describe your experience with performance optimization."]}}

## Round 1: Technical Coding Round 1
**Type:** Data Structures and Algorithms Interview · **Difficulty:** Medium · **Duration:** 45 min
Coding challenge focusing on DS&A.
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 an efficient solution, write clean and correct code, and explain your thought process.
**Interviewers look for:** Strong grasp of data structures and algorithms.; Clean and efficient coding practices.; Problem-solving methodology.; Ability to communicate technical ideas.
**Evaluation criteria:** Correctness of the solution.; Efficiency of the algorithm and data structures used.; Code clarity, style, and maintainability.; Ability to handle edge cases and constraints.
**Common rejection reasons:** Inability to articulate thought process.; Poor understanding of fundamental algorithms.; Inefficient or incorrect code.; Lack of attention to edge cases.
## Questions

- Given an array of integers, find the contiguous subarray with the largest sum.
- Implement a function to reverse a linked list.
- Find the kth smallest element in a binary search tree.

## Preparation tips

- Practice coding problems on platforms like LeetCode.
- Focus on understanding time and space complexity.
- Be prepared to explain your approach before coding.
- Write test cases for your code.

## Round 2: System Design Round
**Type:** System Design Interview · **Difficulty:** Hard · **Duration:** 60 min
Design a scalable system.
This round assesses your ability to design and scale complex systems. You'll be presented with a high-level problem (e.g., designing a social media feed, a URL shortener, or a notification system) and expected to propose a robust and scalable solution. The interviewer will probe your design choices, trade-offs, and understanding of various system components.
**Interviewers look for:** Experience designing large-scale systems.; Understanding of distributed system concepts.; Ability to analyze trade-offs.; Pragmatic approach to problem-solving.
**Evaluation criteria:** Scalability of the proposed design.; Availability and reliability considerations.; Choice of appropriate technologies and trade-offs.; Clarity and completeness of the design.; Ability to handle system failures and constraints.
**Common rejection reasons:** Lack of understanding of distributed systems.; Inability to design scalable solutions.; Poor trade-off analysis.; Not considering failure scenarios.
## Questions

- Design a system like Reddit's front page.
- Design a URL shortening service.
- How would you design a real-time notification system?

## Preparation tips

- Study system design principles (databases, caching, load balancing, message queues).
- Practice designing common systems like Twitter feed, TinyURL, etc.
- Be prepared to discuss trade-offs for each component.
- Think about scalability, availability, and fault tolerance.

## Round 3: Behavioral and Managerial Round
**Type:** Behavioral Interview · **Difficulty:** Medium · **Duration:** 45 min
Assess behavioral competencies and cultural fit.
This round focuses on your past experiences and how you handle various workplace situations. You'll be asked behavioral questions designed to understand your work style, problem-solving approach in non-technical scenarios, teamwork, and leadership potential. Use the STAR method (Situation, Task, Action, Result) to structure your answers.
**Interviewers look for:** Cultural fit.; Collaboration and teamwork skills.; Problem-solving approach in non-technical contexts.; Motivation and passion for Reddit.; Leadership potential.
**Evaluation criteria:** Behavioral competencies (teamwork, leadership, conflict resolution).; Alignment with Reddit's culture and values.; Self-awareness and reflection.; Communication clarity and conciseness.; Motivation and passion for the role.
**Common rejection reasons:** Poor communication skills.; Lack of self-awareness.; Inability to provide specific examples.; Not aligning with company values.; Negative attitude.
## Questions

- Tell me about a time you had a conflict with a colleague and how you resolved it.
- Describe a project you are particularly proud of and your role in it.
- How do you handle constructive criticism?
- Why are you interested in working at Reddit?

## Preparation tips

- Prepare examples using the STAR method for common behavioral questions.
- Reflect on your strengths, weaknesses, and career goals.
- Research Reddit's company values and culture.
- Be ready to discuss your motivations for joining Reddit.