Airtel sde 2

Here is the summary of all questions and answers from the Airtel SDE-2 interview experience:

Interview Overview

Role: SDE-2
Company: Airtel
Mode: Virtual, Google Meet
Duration: Around 90 minutes
Panel: 1 Senior Engineer + 1 Tech Lead
Main focus: Java, Spring Boot, Kafka, System Design, Monitoring, SLA, backend performance

1. Kafka Fundamentals

Question: How does Kafka ensure message delivery guarantees?

Answer summary:

Kafka provides three delivery guarantees:

Important Kafka configs mentioned:

acks=all
min.insync.replicas=2
enable.idempotence=true

  

Key learning: Mention real production configs, not only theory.

2. Monitoring and Observability

Question: How do you track production system performance and uptime?

Answer summary:

Use monitoring and observability tools like:

They configured alerts for:

• Latency spikes

• Downtime anomalies

• Error rate increases

• SLA breaches

Key learning: Always connect tools with metrics like latency, throughput, uptime, and error rate.

3. API SLA and Performance

Question: What is an SLA for an API, and how do you ensure it is met?

Answer summary:

SLA means Service Level Agreement. It defines expected guarantees such as:

• API uptime

• Response time

• Error tolerance

• Availability

Ways to ensure SLA:

They mentioned using Resilience4j for circuit breaker and retry patterns.

Key learning: Don’t only define SLA. Explain how you maintain it in production.

4. Coding Question — Rotated Sorted Array

Question: Find an element in a rotated sorted array.

Example problem:
Given a rotated sorted array and a target, return the index of the target, otherwise return -1.

Brute Force

Check every element one by one.

int search(int[] nums, int target) {
    for (int i = 0; i < nums.length; i++) {
        if (nums[i] == target) return i;
    }
    return -1;
}

  

Time complexity: O(N)

Optimized Approach

Use modified binary search.

int search(int[] nums, int target) {
    int left = 0, right = nums.length - 1;

    while (left <= right) {
        int mid = (left + right) / 2;

        if (nums[mid] == target) return mid;

        if (nums[left] <= nums[mid]) {
            if (target >= nums[left] && target < nums[mid])
                right = mid - 1;
            else
                left = mid + 1;
        } else {
            if (target > nums[mid] && target <= nums[right])
                left = mid + 1;
            else
                right = mid - 1;
        }
    }

    return -1;
}

  

Time complexity: O(log N)

Key learning: First explain brute force, then optimize, then explain why binary search works.

5. System Design Question

Question: Suppose you are tracking the speed of a production line in real time. How would you design the system?

Answer summary:

Proposed architecture:

Devices/Sensors
   ↓
Kafka Topics
   ↓
Spring Boot Consumer Service
   ↓
Processing / Aggregation
   ↓
Time-Series Database
   ↓
Grafana Dashboard
   ↓
Alerting Service

  

Components mentioned:

Important design points:

• Scalability

• Fault tolerance

• Low latency

• Real-time freshness

• Monitoring and alerting

Key learning: For SDE-2, system design should be practical and production-oriented.

6. Project Challenge / Incident Question

Question: Tell me about a major challenge you faced in your project.

Answer summary:

The candidate discussed a payment duplication issue caused by retry loops in a distributed system.

Solution used:

Key learning: Interviewers want to see debugging mindset, ownership, and production experience.

Overall Key Learnings

The interview was more scenario-based than theoretical.

Important areas to prepare:

• Kafka delivery guarantees

• Spring Boot internals

• API SLA and performance

• Monitoring tools like Grafana, Prometheus, ELK

• Resilience4j

• Circuit breaker and retry patterns

• Rotated sorted array / binary search

• Real-time system design

• One strong production incident story

Final Preparation Checklist

For Airtel SDE-2, prepare these:

Best takeaway:
This Airtel SDE-2 interview checks whether you can build, debug, monitor, and scale real backend systems, not just answer textbook definitions.