Ciena SDE-1 Interview Experience (Gurgaon) – Technical Round 1
- Location
- Gurgaon
- Posted
- 19 Mar 2026
Summary
I recently interviewed with Ciena for an SDE-1 (Java Developer) role in Gurgaon. The technical round covered a mix of DSA, Java, Spring Boot, SQL, and system concepts, with a particular focus on Java and Spring Boot.
How it went
The round was a mix of DSA + Java + Spring Boot + SQL + System concepts. But was more focused on java and springboot.
🧠 DSA Questions
1. Longest Substring Without Repeating Characters
Example: abcac → abc → Output: 3
2. Merge Two Sorted Linked Lists
l1: 1 → 3 → 5
l2: 2 → 4 → 6
☕ Java + Spring Boot
Questions asked:
- Difference between
@RestControllervs@Controller - Create a sample API
- Common Spring Boot annotations and how springboot application starts (he was expecting to mention all the annotations)
🗄️ SQL Questions
1. Find second highest salary
2. A follow up question, find second highest unique salary
3. Flip binary values
Table: BINARY_TABLE
0
1
0
Solution:
UPDATE BINARY_TABLE
SET Binary_Column = 1 - Binary_Column;
⚙️ Core Java Concepts
- Java 8 features (Streams, Collections)
- How
HashMapworks internally
📡 Kafka & System Concepts
- Kafka basics
- Partitions and consumers
- Handling high traffic scenarios
Questions asked (13)
- 01
Longest Substring Without Repeating Characters
Data Structures & Algorithms
Given a string, find the length of the longest substring without repeating characters. Example:
abcac→abc→ Output:3 - 02
Merge Two Sorted Linked Lists
Data Structures & Algorithms
Given two sorted linked lists, merge them into a single sorted linked list. Example:
l1: 1 → 3 → 5,l2: 2 → 4 → 6 - 03
Difference between @RestController vs @Controller
Other
Explain the key differences between Spring's
@RestControllerand@Controllerannotations. - 04
Create a Sample REST API
Other
Design and outline how to create a sample REST API, possibly using Spring Boot.
- 05
Spring Boot Annotations and Application Startup Process
Other
Describe common Spring Boot annotations and explain the internal process of how a Spring Boot application starts up, mentioning all relevant annotations.
- 06
Find Second Highest Salary
Other
Write a SQL query to find the second highest salary from a table.
- 07
Find Second Highest Unique Salary
Other
Write a SQL query to find the second highest unique salary from a table.
- 08
Flip Binary Values in a Table
Other
Given a table
BINARY_TABLEwith a column containing binary values (0 or 1), write a SQL query to flip these values (0 becomes 1, 1 becomes 0). Table: BINARY_TABLE 0 1 0 - 09
Java 8 Features (Streams, Collections)
Other
Discuss the significant features introduced in Java 8, specifically focusing on Streams API and enhancements to the Collections framework.
- 10
Internal Working of HashMap
Other
Explain the internal data structures and algorithms that power Java's
HashMap. - 11
Kafka Basics
System Design
Explain the fundamental concepts and architecture of Apache Kafka.
- 12
Kafka Partitions and Consumers
System Design
Discuss Kafka partitions, their purpose, and how consumers interact with them to process messages.
- 13
Handling High Traffic Scenarios
System Design
Describe architectural patterns, strategies, and considerations for designing systems that can effectively handle high traffic and scale accordingly.