# Expert
**Role:** Software Engineer · **Level:** 21
**Company:** [Ozon](https://scaleengineer.com/companies/ozon)
**Difficulty:** Hard
**Salary:** US$150000 - US$200000
**Experience:** 10 - 15
**Timeline:** ~14 days
This interview process is designed to assess candidates for an Expert Software Engineer role at Ozon, level 21. It evaluates deep technical expertise, problem-solving abilities, system design skills, and leadership potential.
Canonical: https://scaleengineer.com/interviews/ozon/21-software-engineer
---
## Overall evaluation

- Technical Proficiency
- System Design
- Leadership and Impact
- Communication

## Questions asked

- Design a URL shortening service.
- How would you design a system to handle real-time analytics for a streaming service?
- Describe a situation where you had to deal with a major production incident. What was your role, and what did you learn?
- What are the trade-offs between SQL and NoSQL databases for a large-scale application?
- How do you approach performance tuning in a distributed system?
- Tell me about a time you disagreed with a technical decision made by your team or manager. How did you handle it?
- What are your thoughts on containerization and orchestration technologies like Docker and Kubernetes?
- How would you design a notification system for a social media platform?
- Explain the concept of eventual consistency and provide an example.
- Describe your experience with cloud platforms like AWS, Azure, or GCP.

## Preparation tips

### lists

- Review core computer science fundamentals, including data structures, algorithms, and operating systems.
- Deep dive into distributed systems concepts, such as consensus algorithms, message queues, and caching strategies.
- Practice system design problems, focusing on scalability, reliability, and performance.
- Prepare to discuss your past projects in detail, highlighting your technical contributions and impact.
- Familiarize yourself with Ozon's products, services, and technology stack.
- Brush up on behavioral interview techniques, using the STAR method (Situation, Task, Action, Result).
- Prepare questions to ask the interviewers about the role, team, and company culture.

### studyPlan

- {"title":"Data Structures and Algorithms","longDescription":"Weeks 1-2: Focus on Data Structures and Algorithms. Review common algorithms (sorting, searching, graph traversal) and data structures (arrays, linked lists, trees, hash maps). Practice problems on platforms like LeetCode, HackerRank, focusing on medium to hard difficulty.","shortDescription":"Weeks 1-2: DSA fundamentals and practice (LeetCode medium/hard)."}
- {"title":"System Design","longDescription":"Weeks 3-4: Dive into System Design. Study concepts like load balancing, database scaling, caching, microservices architecture, API design, and fault tolerance. Read relevant books and articles, and work through system design case studies.","shortDescription":"Weeks 3-4: System Design principles and case studies."}
- {"title":"Distributed Systems","longDescription":"Week 5: Focus on Distributed Systems. Understand concepts like CAP theorem, eventual consistency, distributed transactions, and message queuing systems. Explore specific technologies like Kafka, RabbitMQ, and distributed databases.","shortDescription":"Week 5: Distributed Systems concepts and technologies."}
- {"title":"Behavioral and Leadership","longDescription":"Week 6: Behavioral and Leadership. Prepare examples of your leadership experience, problem-solving skills, and teamwork. Reflect on your career achievements and how they align with Ozon's values. Practice answering common behavioral questions.","shortDescription":"Week 6: Behavioral and Leadership preparation."}
- {"title":"Company Research & Mock Interviews","longDescription":"Week 7: Ozon Specifics and Mock Interviews. Research Ozon's business, products, and recent news. Conduct mock interviews with peers or mentors to simulate the interview environment and get feedback.","shortDescription":"Week 7: Company research and mock interviews."}

## Location differences

- {"location":"Moscow","differences":{"tips":["Be prepared to discuss your contributions to open-source projects.","Highlight instances where you influenced technical direction or strategy.","Showcase your ability to handle ambiguity and drive projects to completion.","Emphasize your experience with large-scale data processing and analytics."],"interviewFocus":["Deep understanding of distributed systems and scalability.","Proven ability to lead technical initiatives and mentor teams.","Experience with cloud-native architectures and microservices.","Strong problem-solving and debugging skills in complex environments."],"commonQuestions":["How would you design a distributed caching system for a large e-commerce platform?","Describe a complex technical challenge you faced and how you overcame it.","Discuss your experience with performance optimization in high-traffic systems.","What are your strategies for mentoring junior engineers?","How do you stay updated with the latest technologies and trends in software engineering?"]}}
- {"location":"Saint Petersburg","differences":{"tips":["Research Ozon's recent technological advancements and product launches.","Prepare specific examples of how you've improved system performance or reduced operational costs.","Be ready to discuss your leadership style and how you foster a positive team environment.","Demonstrate a proactive approach to identifying and solving technical problems."],"interviewFocus":["Expertise in specific technology stacks relevant to Ozon's current projects.","Ability to architect and implement robust and scalable solutions.","Experience with agile methodologies and DevOps practices.","Strong communication and collaboration skills."],"commonQuestions":["Design a real-time recommendation engine for an online marketplace.","Explain the trade-offs between different database technologies for a specific use case.","How would you ensure the reliability and fault tolerance of a critical service?","Describe your approach to code reviews and maintaining code quality.","What are your thoughts on the future of AI in software development?"]}}

## Round 1: Technical Round 1: Algorithms and Data Structures
**Type:** Data Structures and Algorithms · **Difficulty:** Hard · **Duration:** 60 min
Assess core CS knowledge through coding challenges.
This round focuses on your fundamental computer science knowledge. You will be asked to solve algorithmic problems, often involving data structures. The interviewer will assess your ability to analyze problems, devise efficient solutions, and write clean, working code. Expect questions that test your understanding of time and space complexity.
**Interviewers look for:** Strong grasp of data structures and algorithms.; Ability to translate requirements into efficient code.; Clear thinking and logical reasoning.
**Evaluation criteria:** Correctness and efficiency of algorithms.; Understanding of time and space complexity.; Problem-solving approach.; Coding proficiency.
**Common rejection reasons:** Lack of fundamental understanding in core CS concepts.; Inability to articulate thought process clearly.; Poorly designed solutions that do not scale or are not robust.
## Questions

- Given a binary tree, find the lowest common ancestor of two given nodes.
- Implement a function to find the k-th largest element in an unsorted array.
- Design a data structure that supports insertion, deletion, and getRandom in O(1) time.

## Preparation tips

- Practice coding problems regularly.
- Understand the time and space complexity of your solutions.
- Be able to explain your thought process clearly.
- Write clean and well-structured code.

## Round 2: Technical Round 2: System Design
**Type:** System Design · **Difficulty:** Hard · **Duration:** 75 min
Assess ability to design scalable and robust software systems.
This round evaluates your ability to design complex software systems. You'll be presented with a high-level problem (e.g., design a social media feed, a ride-sharing service) and expected to propose a scalable, reliable, and maintainable architecture. Focus on identifying components, data flow, APIs, database choices, and potential bottlenecks.
**Interviewers look for:** Experience designing complex, large-scale systems.; Deep understanding of distributed systems principles.; Ability to think critically about system design choices.; Pragmatic approach to problem-solving.
**Evaluation criteria:** Scalability of the proposed solution.; Reliability and fault tolerance.; Understanding of system components and interactions.; Ability to handle trade-offs.; Knowledge of relevant technologies.
**Common rejection reasons:** Inability to design scalable and reliable systems.; Poor understanding of trade-offs in architectural decisions.; Lack of experience with distributed systems concepts.
## Questions

- Design a distributed key-value store.
- Design a rate limiter for an API.
- Design a system to count unique visitors to a website in real-time.

## Preparation tips

- Study common system design patterns.
- Understand trade-offs between different technologies.
- Practice designing systems for scale and reliability.
- Be prepared to justify your design decisions.

## Round 3: Managerial Round: Behavioral and Leadership
**Type:** Behavioral Interview · **Difficulty:** Medium · **Duration:** 45 min
Assess behavioral traits, leadership, and cultural fit.
This round focuses on your behavioral and leadership qualities. You'll be asked about your past experiences, how you handle challenges, work with others, and your career aspirations. The interviewer aims to understand your personality, motivation, and how you would fit into the team and company culture.
**Interviewers look for:** Ability to work effectively in a team.; Proactive attitude and ownership.; Clear communication of ideas and experiences.; Alignment with Ozon's values.
**Evaluation criteria:** Communication clarity.; Problem-solving approach.; Teamwork and collaboration.; Leadership potential.; Cultural alignment.
**Common rejection reasons:** Poor communication skills.; Lack of leadership or initiative.; Inability to articulate past experiences effectively.; Poor cultural fit.
## Questions

- Tell me about a time you had to lead a project. What were the challenges, and how did you overcome them?
- Describe a situation where you had a conflict with a colleague. How did you resolve it?
- Why are you interested in working at Ozon?

## Preparation tips

- Prepare specific examples using the STAR method.
- Reflect on your strengths and weaknesses.
- Think about your career goals and why you're interested in Ozon.
- Be enthusiastic and genuine.

## Round 4: Final Round: Strategic and Leadership Vision
**Type:** Executive/Leadership Interview · **Difficulty:** Hard · **Duration:** 60 min
Assess strategic thinking and leadership vision with senior management.
This final round is with senior leadership and focuses on your strategic thinking, technical vision, and potential to influence the engineering organization. Expect questions about your career philosophy, how you approach technical challenges at a high level, and your thoughts on the future of technology and Ozon's role within it.
**Interviewers look for:** Proven track record of technical leadership.; Ability to think about the bigger picture and long-term impact.; Experience mentoring and growing engineering teams.; Deep technical expertise and passion.
**Evaluation criteria:** Strategic thinking and vision.; Technical leadership and influence.; Ability to drive innovation.; Mentorship capabilities.; Communication of complex ideas.
**Common rejection reasons:** Lack of strategic thinking.; Inability to influence technical direction.; Poor communication of high-level concepts.; Not demonstrating senior-level impact.
## Questions

- What is your philosophy on building high-performing engineering teams?
- How do you stay ahead of technological trends and ensure your team does the same?
- Imagine you are tasked with improving the overall engineering productivity at Ozon. What would be your first steps?

## Preparation tips

- Think about your long-term career goals.
- Consider how you can contribute to Ozon's strategic objectives.
- Be prepared to discuss your vision for technology and engineering.
- Showcase your passion for technology and innovation.