Apache Flink Interview Questions for Freshers Candidates

👶 Apache Flink Interview Questions for Freshers

Here’s a list of common Flink interview questions for freshers, often asked when the candidate is new to stream processing or just starting with Flink.

🔹 Basic Flink Concepts

1. What is Apache Flink?
2. What are the main features of Flink?
3. How is Flink different from Spark Streaming or Kafka Streams?
4. What are stream processing and batch processing?
5. What are some real-world use cases of Flink?

🔹 Programming & API Basics

1. What is the DataStream API in Flink?
2. What is the difference between the DataSet and DataStream API?
3. How do you create a Flink job?
4. How do you define a source and sink in Flink?
5. Can you write a simple Flink job to filter even numbers from a stream?

🔹 Time & Event Handling

1. What is event time vs processing time?
2. What are watermarks in Flink?
3. Why is event time processing important in real-time systems?

🔹 Windowing Basics

1. What are windows in Flink?
2. What’s the difference between tumbling and sliding windows?
3. Give an example of a use case where windowing is useful.

🔹 Fault Tolerance (Basic Level)

1. What is checkpointing in Flink?
2. Why is state management important in stream processing?
3. What is the difference between at-least-once and exactly-once semantics?

🔹 General Java & Integration Questions (If Needed)

1. Which language did you use for writing Flink jobs—Java or Scala?
2. How do you integrate Flink with Kafka (or any source)?
3. Have you worked on any mini-projects using Flink? What was your role?

✅ Tips for Freshers:

• Be clear on stream processing fundamentals (e.g., unbounded data, windows, watermarks).
• Practice writing very simple Flink jobs using Java.
• If you’ve done a project—even a mini one—describe the flow clearly (source → process → sink).
• Even if you haven’t worked on Flink professionally, interviewers appreciate clarity and curiosity.

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