Scale Engineer

Principal Software Engineer

Software EngineerL7Hard

The Principal Software Engineer (L7) interview at Criteo is a rigorous process designed to assess deep technical expertise, leadership potential, and strategic thinking. Candidates are expected to demonstrate a strong command of software engineering principles, experience in designing and scaling complex systems, and the ability to mentor and guide other engineers. The interview process typically involves multiple rounds, including technical deep dives, system design, behavioral assessments, and a final discussion with senior leadership.

Rounds·4

Timeline·~14d

Experience·8 - 15 yrs

Comp band·US$170000 - US$220000

Interview time·225 min

Evaluation

What they measure.

  • Technical depth and breadth
  • Problem-solving skills
  • System design and architecture
  • Scalability and performance considerations
  • Leadership and mentorship
  • Communication and collaboration
  • Cultural fit and alignment with Criteo's values

Preparation

How to prepare.

Tips

  1. Deeply understand Criteo's business, products, and technology stack.
  2. Review fundamental computer science concepts (data structures, algorithms, operating systems, networking).
  3. Practice system design problems, focusing on scalability, reliability, and trade-offs.
  4. Prepare specific examples from your past experience that demonstrate leadership, problem-solving, and impact.
  5. Familiarize yourself with common ad-tech concepts and challenges.
  6. Practice articulating your thought process clearly and concisely.
  7. Research the interviewers on LinkedIn to understand their backgrounds.

Study plan

Fig · Study plan — 04 phases

01 / 04
01

Phase 01 of 04

Data Structures & Algorithms

Weeks 1-2: DSA fundamentals. LeetCode (Medium/Hard).

Weeks 1-2: Focus on core data structures and algorithms. Review common patterns and complexity analysis. Practice problems on platforms like LeetCode (Medium/Hard).

Questions

Commonly asked.

  • Design a distributed caching system for a high-traffic website.
  • How would you optimize the performance of a slow-running API?
  • Describe a time you had to influence a team's technical direction.
  • What are the trade-offs between SQL and NoSQL databases for a specific use case?
  • How do you approach mentoring junior engineers?
  • Tell me about a complex technical problem you solved.
  • How would you design a system to detect fraudulent ad clicks?
  • What are your thoughts on microservices vs. monolith architectures?
  • Describe your experience with cloud platforms like AWS, Azure, or GCP.
  • How do you handle technical debt?
  • What is your approach to code reviews?
  • How do you stay up-to-date with new technologies?

Locations

Regional differences.

Fig · Regions — 03 locations

01 / 03

Location

Paris

Interview focus

Emphasis on distributed systems design and scalability.Assessment of leadership and mentorship capabilities.Evaluation of strategic thinking and long-term technical vision.

Common questions

  • How would you design a real-time bidding system for online advertising?
  • Discuss a time you had to make a significant technical trade-off. What was the outcome?
  • How do you approach performance optimization in a large-scale distributed system?
  • Describe your experience with cloud-native architectures (e.g., Kubernetes, microservices).

Tips

  • Be prepared to discuss your contributions to open-source projects.
  • Highlight experience with high-traffic, low-latency systems.
  • Showcase your ability to influence technical direction and mentor junior engineers.

Rounds

Round-by-round.

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

DSA

Coding questions at Criteo.

Frequently reported on Criteo loops

View all at Criteo

Other guides

More at Criteo.