Fortinet | SDE | Backend | Dec 2025 | Offer
Prior experience: ~3years (Product based Company)
College: Tier-1
Location: Bangalore
Date: Dec 2025
Process: I have taken referral and got call from HR. There were total 5 technical and 1 HR rounds.
Round 1 - Online Assessment (OA)
What was asked:
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One incomplete REST API where I had to implement a missing feature using Java + Spring Boot
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5 SQL questions (queries, joins, basic DB understanding)
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5 CS fundamentals questions (OOPS, basics of OS/DB)
This round tested practical backend understanding, not just theory.
Round 2 - Backend & CS Fundamentals
The interviewer started by going through my resume.
One line from my resume caught his attention: “ORM optimization”.
From there, he asked many questions one after another to check how well I actually understood backend concepts.
Topics discussed:
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What is ORM and why we use it
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How ORM can be optimized
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Lazy loading vs eager loading
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SQL indexing and joins
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Schema design
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One SQL query
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SQL injection and how ORM helps prevent it
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Other backend security issues
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Kafka basics
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OAuth 2.0 basics
The ORM discussion went very deep, and the idea was to check whether I had real hands-on experience or just theoretical knowledge.
I was able to answer most of the questions, but after many follow-ups, I finally gave up 😄.
At the end, there was a coding question.
This round was long, intense, and very detailed.
Round 3 - Coding
Problems asked:
- Pascal’s Triangle - https://leetcode.com/problems/pascals-triangle/description/
- Best Time to Buy and Sell Stock II https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/description/
Round 4 - HLD + Coding
- Coding: Reverse string without extra space
The interviewer asked me to explain the architecture of one of my projects that I had worked on.
The discussion went deep into:
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Why I chose this design
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What trade-offs were involved
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What would happen in failure cases
Questions included:
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Writing pseudo-code for a pub-sub consumer
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How async calls were handled
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What happens if:
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- Consumer is down
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- Message queue is down
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How APIs are secured
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How large traffic is controlled
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How CSRF attacks are handled
Learning from this round:
You should clearly understand everything you mention in your project.
They can easily tell if you’ve really worked on it or not.
Round 5 - System Design
This round was fully focused on design.
Topics discussed:
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Architecture of my master’s project
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OAuth 2.0 in depth
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Discussion on Rate limiter algorithms
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Recovery services
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How services communicate with each other
This was a tight and challenging round.
Round 6 – HR Round
This was a relaxed discussion:
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Why Fortinet?
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What kind of work I’m interested in
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Expectations from the role
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General behavioral questions
SUMMARY :
The interview process was challenging but fair, with a strong focus on backend fundamentals, system design, and real project experience. Fortinet interviewers go very deep into discussions, so one key takeaway is that you must know everything written on your resume in depth, as even a single line can lead to detailed follow-up questions. Overall, it was a great learning experience
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**Happy to help :)
Feel free to check my profile for more discussions.
