Blinkit SDE-1 Backend Interview Experience | Off-Campus
Summary
I was selected for the Blinkit SDE-1 Backend role after passing three interview rounds (DSA, system design, and cultural fit) and received the offer during the final interview.
Full Experience
Blinkit SDE-1 Backend Interview Experience | Off-Campus
Sharing my Blinkit SDE-1 Backend interview experience for anyone preparing for similar roles.
Role: SDE-1 Backend Hiring: Off-Campus Interview Process: 3 Rounds - DSA -> LLD/System Design -> Cultural Fitment Final Result: Selected Location: Gurgaon
How I Got the Interview
I received a call from a Blinkit HR completely out of the blue. She asked about:
- Where I was currently working
- My notice period
- Current location
She then mentioned that they liked my profile and wanted to schedule an interview.
The process consisted of 3 rounds:
- DSA
- System Design / LLD
- Cultural Fitment
Round 1 - DSA
The round was taken by an SDE-3.
He started with a great introduction about himself and his team. We then discussed my previous experience and projects.
Before jumping into DSA, he asked several questions to check my understanding of CS fundamentals and backend internals.
Technical questions
Some of the questions discussed were:
- Stack and memory
- What is stored in stack?
- What happens internally when another function is called?
- How are function calls handled?
- Map internals
- How does a Map/HashMap work internally?
- How are keys stored and retrieved?
- What happens during collisions?
- Database indexing
- How does indexing work internally?
- What data structure is generally used?
- How does an index improve query performance?
After that, we moved to coding problems.
Problem 1 - Find Peak Element
He asked me to find a peak element in an array.
I was able to identify the binary search approach within about a minute and explained the intuition.
I then wrote the pseudocode and discussed the complexity.
Problem 2 - Design an LFU Cache
The next problem was to design an LFU Cache, specifically focusing on the put() and get() operations.
I explained the data structures and approach, wrote the pseudocode, and did a dry run with an example.
The interviewer seemed satisfied with the approach.
We then spent some time discussing the work culture and I asked a few questions about the team and role.
Round 2 - LLD / System Design
The second round was taken by a Team Lead.
We again started with introductions, followed by a discussion about my experience and projects.
He then gave me the following design problem:
Design a Notification System
This was primarily a design discussion rather than a coding round.
We used draw.io to create UML diagrams and discuss the architecture.
The interviewer focused heavily on my design decisions and trade‑offs rather than just asking me to draw a solution.
Some of the areas we discussed were:
- Designing the notification flow
- Choosing appropriate APIs/queries
- Database design
- Indexing
- Kafka vs APIs
- Scalability considerations
- Different components of the system
- Trade‑offs behind different architectural decisions
- Various HLD concepts
A major part of the round was explaining why I was choosing a particular approach and what alternatives were available.
I personally felt that I didn't give my best in this round, especially compared to how I wanted the discussion to go.
However, I was later contacted by HR for the next round, so I knew I had cleared it.
Round 3 - Cultural Fitment
The final round was with the Manager.
We started with introductions and then went through my resume in detail.
There was a deeper discussion around:
- My previous experience
- Projects
- Technologies I had worked with
- My role and responsibilities
- Technical decisions I had made
After that, the conversation moved towards behavioral and cultural‑fit questions.
The round was relatively conversational rather than being a traditional technical interview.
After around 20 minutes, the manager told me that he was happy with my performance and gave me the offer during the round itself.
Final Result
Selected for Blinkit SDE-1 Backend!
Edit: I am 2026 Graduate and I have intern exp of 6 months
Interview Questions (3)
Find Peak Element
Given an array, find an index i such that arr[i] is greater than or equal to its neighbors. The element at the boundaries has only one neighbor. Return any peak element's index. The expected solution uses a binary search approach with O(log n) time complexity.
Design LFU Cache
Design a Least Frequently Used (LFU) cache that supports get(key) and put(key, value) operations. Both operations should have O(1) time complexity. The cache should evict the least frequently used item when capacity is reached, and in case of ties, the least recently used among them.
Design a Notification System
Create a notification system that can send real‑time alerts to users. Discuss components such as API endpoints, message queues (e.g., Kafka), database schema, indexing strategy, scalability, and fault tolerance. Produce high‑level UML diagrams and justify design choices.