# Software Engineer
**Role:** Software Engineer · **Level:** L2
**Company:** [Criteo](https://scaleengineer.com/companies/criteo)
**Difficulty:** Medium
**Salary:** US$100000 - US$130000
**Experience:** 2 - 5
**Timeline:** ~7 days
The Software Engineer L2 interview at Criteo is designed to assess a candidate's technical proficiency, problem-solving abilities, and cultural fit within the company. It typically involves multiple rounds, including technical assessments, behavioral questions, and a discussion about past projects and experiences. The goal is to identify candidates who can contribute effectively to Criteo's engineering teams and uphold the company's values.
Canonical: https://scaleengineer.com/interviews/criteo/l2-software-engineer
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## Overall evaluation

- Technical Skills
- Communication and Collaboration
- Experience and Motivation

## Questions asked

- Write a function to find the kth largest element in an unsorted array.
- Design a URL shortening service like bit.ly.
- Tell me about a time you disagreed with a technical decision made by your team. What did you do?
- How would you optimize a slow database query?
- Explain the difference between a process and a thread.
- Describe a situation where you had to mentor a junior engineer.
- How do you handle production issues under pressure?
- Design a system to handle real-time analytics for a website.
- What are the trade-offs between monolithic and microservices architectures?
- Tell me about a bug you introduced and how you fixed it.

## Preparation tips

### lists

- Review fundamental computer science concepts (data structures, algorithms, complexity analysis).
- Practice coding problems on platforms like LeetCode or HackerRank, focusing on medium-difficulty problems.
- Prepare to discuss your past projects in detail, highlighting your contributions and the challenges you faced.
- Brush up on system design principles, especially those relevant to Criteo's business (e.g., ad tech, real-time bidding, large-scale data processing).
- Understand Criteo's company culture, values, and recent news.
- Prepare behavioral questions using the STAR method (Situation, Task, Action, Result).
- Think about questions you want to ask the interviewer about the role, team, and company.

### studyPlan

- {"title":"Data Structures and Algorithms","longDescription":"Weeks 1-2: Focus on Data Structures and Algorithms. Cover arrays, linked lists, trees, graphs, hash tables, heaps, sorting, searching, dynamic programming, and greedy algorithms. Practice problems related to each topic, aiming for 2-3 problems per day. Understand time and space complexity analysis.","shortDescription":"Weeks 1-2: DSA fundamentals and practice (2-3 problems/day)."}
- {"title":"System Design","longDescription":"Weeks 3-4: System Design and Scalability. Study concepts like load balancing, caching, database design (SQL vs. NoSQL), message queues, microservices architecture, and API design. Read case studies and practice designing scalable systems. Focus on trade-offs and justifications.","shortDescription":"Weeks 3-4: System Design principles and case studies."}
- {"title":"Behavioral and Project Experience","longDescription":"Week 5: Behavioral and Project Deep Dive. Prepare to discuss your resume projects in detail. Use the STAR method to structure your answers for behavioral questions related to teamwork, problem-solving, conflict resolution, and leadership. Reflect on your career goals and motivations.","shortDescription":"Week 5: Behavioral questions (STAR method) and resume project review."}
- {"title":"Mock Interviews and Refinement","longDescription":"Week 6: Mock Interviews and Refinement. Conduct mock interviews with peers or mentors to simulate the actual interview environment. Focus on improving communication, clarity of thought, and time management. Review any weak areas identified during practice.","shortDescription":"Week 6: Mock interviews and final review."}

## Location differences

- {"location":"Paris","differences":{"tips":["Be prepared to discuss specific examples from your past projects.","Clearly articulate your thought process when solving problems.","Showcase your ability to work effectively in a team environment.","Research Criteo's tech stack and recent projects."],"interviewFocus":["Emphasis on practical problem-solving and debugging skills.","Assessment of collaboration and communication within a team.","Understanding of distributed systems and scalability principles."],"commonQuestions":["Describe a challenging technical problem you solved at your previous company.","How do you approach debugging a complex issue?","Tell me about a time you had to work with a difficult team member.","What are your thoughts on microservices architecture?","How do you ensure the scalability of your code?"]}}
- {"location":"New York","differences":{"tips":["Provide concrete examples to support your answers.","Demonstrate a proactive approach to learning and problem-solving.","Be honest about your strengths and weaknesses, and show how you are working on them.","Highlight any experience with large-scale systems or high-traffic applications."],"interviewFocus":["Evaluation of adaptability and learning agility.","Assessment of self-awareness and professional development.","Understanding of fundamental web technologies and best practices."],"commonQuestions":["How do you handle tight deadlines and pressure?","Describe a situation where you had to adapt to a new technology quickly.","What are your strengths and weaknesses as a software engineer?","How do you stay updated with the latest industry trends?","Explain the concept of RESTful APIs."]}}

## Round 1: Data Structures and Algorithms
**Type:** Technical Interview (Coding) · **Difficulty:** Medium · **Duration:** 45 min
Coding challenges to assess DSA proficiency.
This round focuses on assessing your core technical skills through coding challenges. You will be asked to solve 1-2 problems related to data structures and algorithms. The interviewer will evaluate your ability to understand the problem, devise an efficient solution, write clean code, and explain your approach. Expect questions on arrays, strings, linked lists, trees, graphs, dynamic programming, and sorting/searching algorithms.
**Interviewers look for:** Strong grasp of DSA; Ability to translate requirements into code; Logical thinking and systematic approach; Clear communication of thought process
**Evaluation criteria:** Correctness of the solution; Efficiency of the solution (time and space complexity); Code quality and readability; Problem-solving approach; Communication of the solution
**Common rejection reasons:** Inability to solve coding problems within the given time.; Poor understanding of fundamental data structures and algorithms.; Lack of clarity in explaining the thought process.; Inability to write clean, efficient, and bug-free code.
## Questions

- Given a binary tree, find its inorder traversal.
- Implement a function to check if a string is a palindrome, ignoring non-alphanumeric characters and case.
- Find the first non-repeating character in a string.

## Preparation tips

- Practice coding problems on platforms like LeetCode, HackerRank, or Coderbyte.
- Focus on understanding the underlying algorithms and data structures.
- Practice explaining your thought process out loud while solving problems.
- Write clean, well-commented code.
- Be prepared to discuss time and space complexity.

## Round 2: System Design and Architecture
**Type:** System Design Interview · **Difficulty:** Medium · **Duration:** 60 min
Design scalable software systems and discuss trade-offs.
This round evaluates your ability to design and architect software systems. You'll be presented with a high-level problem (e.g., design a URL shortener, a social media feed, or a rate limiter) and asked to propose a solution. The focus is on scalability, reliability, performance, and trade-offs. You should be prepared to discuss database choices, caching strategies, API design, and potential bottlenecks.
**Interviewers look for:** System thinking; Knowledge of distributed systems; Ability to design for scale; Pragmatic approach to problem-solving
**Evaluation criteria:** Ability to design scalable and reliable systems; Understanding of system components (databases, caches, load balancers, APIs); Trade-off analysis and justification; Handling of edge cases and failure scenarios; Clarity of design and communication
**Common rejection reasons:** Lack of understanding of system design principles.; Inability to handle scale and performance considerations.; Poor trade-off analysis.; Difficulty in breaking down complex problems into manageable components.
## Questions

- Design a system to count the number of views for a given YouTube video.
- Design a distributed cache system.
- How would you design a system to detect duplicate uploads of images?

## Preparation tips

- Study common system design patterns and concepts.
- Read system design case studies and blogs.
- Practice designing systems for scale.
- Be prepared to justify your design choices and discuss trade-offs.
- Consider different components like databases, caches, load balancers, message queues, and CDNs.

## Round 3: Behavioral and Cultural Fit
**Type:** Behavioral Interview · **Difficulty:** Medium · **Duration:** 45 min
Assess past experiences, behavioral competencies, and cultural fit.
This round focuses on your past experiences, behavioral competencies, and cultural fit. You'll be asked questions about how you've handled specific situations in previous roles, such as dealing with conflict, managing challenging projects, or working in a team. The interviewer wants to understand your working style, your strengths and weaknesses, and how you align with Criteo's values. Be prepared to share specific examples using the STAR method.
**Interviewers look for:** Teamwork and collaboration skills; Problem-solving approach in real-world scenarios; Adaptability and resilience; Cultural alignment; Passion and drive
**Evaluation criteria:** Behavioral competencies (teamwork, problem-solving, adaptability); Communication clarity and effectiveness; Self-awareness and reflection; Alignment with Criteo's values; Motivation and passion for the role
**Common rejection reasons:** Poor communication skills.; Lack of self-awareness.; Inability to provide specific examples.; Negative attitude or lack of enthusiasm.; Poor cultural fit.
## Questions

- Tell me about a time you failed. What did you learn from it?
- Describe a situation where you had to work with a difficult colleague. How did you handle it?
- How do you prioritize your work when you have multiple competing deadlines?

## Preparation tips

- Review your resume and prepare specific examples for common behavioral questions.
- Use the STAR method (Situation, Task, Action, Result) to structure your answers.
- Reflect on your strengths, weaknesses, career goals, and motivations.
- Research Criteo's company culture and values.
- Be enthusiastic and genuine in your responses.