Kubernetes | Docker | Spring Boot | Observability | SQL | Programming
Duration: 20 Minutes
Experience: 5–10 Years
This assessment evaluates practical Kubernetes, Docker, Spring Boot production deployment, observability, configuration management, health checks, SQL, and Java 8 programming concepts commonly used in cloud-native backend applications.
Section A – Kubernetes & Docker MCQs (5 Questions)
Question 1 – Kubernetes Self-Healing
A Spring Boot application is deployed with 3 replicas in Kubernetes. One pod crashes because of an OutOfMemoryError.
What happens?
A. Kubernetes permanently removes the application.
B. Kubernetes automatically creates a replacement pod to maintain the desired replica count.
C. All remaining pods are restarted.
D. Traffic is routed only to the failed pod.
Question 2 – ConfigMap vs Secret
Which Kubernetes resource should be used to store a database password?
A. ConfigMap
B. Secret
C. Deployment
D. Service
Question 3 – Readiness Probe
What is the primary purpose of a Readiness Probe?
A. Restart the application if it crashes.
B. Determine whether a pod is ready to receive traffic.
C. Monitor CPU utilization.
D. Scale pods automatically.
Question 4 – Docker Layers
Which statement about Docker images is TRUE?
A. Every container shares the image’s read-only layers and has its own writable layer.
B. Every container creates a completely new image.
C. Docker images cannot contain multiple layers.
D. Docker containers cannot share image layers.
Question 5 – Spring Boot Actuator
Which endpoint is commonly used by Kubernetes for liveness and readiness checks?
A.
/api/status
B.
/actuator/health
C.
/metrics
D.
/status
Section B – SQL Challenge
Question 6
Tables
ORDERS
| ORDER_ID | CUSTOMER_ID | STATUS |
|---|---|---|
| 101 | 1 | SUCCESS |
| 102 | 1 | FAILED |
| 103 | 2 | SUCCESS |
| 104 | 2 | SUCCESS |
| 105 | 3 | FAILED |
Query
SELECT STATUS,
COUNT(*)
FROM ORDERS
GROUP BY STATUS;
What is the correct output?
A.
SUCCESS 3
FAILED 2
B.
SUCCESS 2
FAILED 3
C.
SUCCESS 5
D.
Compilation Error
Section C – Programming Questions
Question 7 – Top 3 Highest Numbers
Given
List<Integer> list =
Arrays.asList(4,8,2,10,7,9,10,8,6);
Using Java 8 Streams:
- Remove duplicates.
- Print the top 3 highest numbers.
Expected Output
10
9
8
Question 8 – Employee Salary Statistics
Given
class Employee{
private String department;
private int salary;
}
Using Java 8 Streams, calculate:
- Minimum salary per department
- Maximum salary per department
- Average salary per department
Question 9 – First Repeating Word
Write a Java program to find the first repeating word in a sentence.
Example
Java Spring Boot Java Microservices Spring
Expected Output
Java
Bonus:
Provide both a traditional solution and a Java 8 Streams solution.
Answer Key & Detailed Explanations
Question 1
Correct Answer: B
Explanation
Kubernetes continuously compares the desired state with the actual state.
If the Deployment specifies:
Replicas = 3
and one pod crashes, Kubernetes automatically schedules a replacement pod to restore the replica count.
This is known as self-healing.
Interview Follow-up
- Which Kubernetes controller manages replica count?
- Difference between a Deployment and a ReplicaSet?
(Expected answer: Deployment manages ReplicaSets, and ReplicaSets maintain the desired number of Pods.)
Question 2
Correct Answer: B
Explanation
Sensitive information such as:
- Database passwords
- API keys
- OAuth tokens
- Certificates
should be stored in Secrets.
Configuration values that are not sensitive (URLs, feature flags, application settings) belong in ConfigMaps.
Question 3
Correct Answer: B
Explanation
A Readiness Probe determines whether the application is ready to serve requests.
If the readiness probe fails:
- The pod continues running.
- Kubernetes removes the pod from the Service endpoints.
- No new traffic is routed to it until it becomes ready again.
Question 4
Correct Answer: A
Explanation
Docker images consist of multiple immutable layers.
Each running container adds its own writable layer on top of the shared read-only image layers.
This design reduces storage usage and speeds up container startup.
Question 5
Correct Answer: B
Explanation
Spring Boot Actuator exposes:
/actuator/health
Kubernetes commonly configures:
- Liveness Probe
- Readiness Probe
to call this endpoint.
Modern Spring Boot versions also support:
/actuator/health/liveness
/actuator/health/readiness
Question 6
Correct Answer: A
Explanation
Order counts:
| Status | Count |
|---|---|
| SUCCESS | 3 |
| FAILED | 2 |
Output
SUCCESS 3
FAILED 2
Question 7 – Sample Solution
list.stream()
.distinct()
.sorted(Comparator.reverseOrder())
.limit(3)
.forEach(System.out::println);
Concepts Tested
distinct()sorted()limit()- Streams
Complexity
Time: O(n log n)
Space: O(n)
Interview Follow-up
Can you solve this in O(n) without sorting?
(Expected answer: Yes, by maintaining the top three distinct values in a single pass.)
Question 8 – Sample Solution
Map<String, IntSummaryStatistics> stats =
employees.stream()
.collect(Collectors.groupingBy(
Employee::getDepartment,
Collectors.summarizingInt(Employee::getSalary)));
stats.forEach((dept, summary) -> {
System.out.println(dept);
System.out.println("Min : " + summary.getMin());
System.out.println("Max : " + summary.getMax());
System.out.println("Avg : " + summary.getAverage());
});
Concepts Tested
groupingBy()summarizingInt()IntSummaryStatistics
Complexity
Time: O(n)
Space: O(n)
Question 9 – Sample Solution
Traditional
Set<String> seen = new HashSet<>();
for(String word : sentence.split(" ")){
if(!seen.add(word)){
System.out.println(word);
break;
}
}
Java 8
Set<String> seen = new HashSet<>();
Arrays.stream(sentence.split(" "))
.filter(word -> !seen.add(word))
.findFirst()
.ifPresent(System.out::println);
Complexity
Time: O(n)
Space: O(n)
Evaluation Guide
| Score | Recommendation |
|---|---|
| 9/9 | Excellent – Strong Cloud-Native Java Developer |
| 7–8 | Good – Proceed to Technical Round |
| 5–6 | Average – Requires Further Evaluation |
| Below 5 | Not Recommended |
Interviewer’s Notes
This set focuses on production operations and deployment concepts that backend engineers encounter in Kubernetes-based environments.
A strong candidate should be able to explain:
- How Kubernetes self-healing works using Deployments and ReplicaSets.
- The difference between ConfigMaps and Secrets.
- The purpose of Readiness and Liveness probes and when each is triggered.
- Docker image layering and why containers start quickly.
- How Spring Boot Actuator integrates with Kubernetes health checks.
- How
summarizingInt()simplifies aggregation logic. - The time and space complexity of each programming solution.
Candidates who additionally discuss rolling updates, blue-green deployments, canary releases, Horizontal Pod Autoscaler (HPA), graceful shutdown, resource requests and limits, and observability with Prometheus/Grafana typically demonstrate strong production experience with Kubernetes.
