Apexon Interview Questions

I recently went through the Apexon Software Engineer interview. Instead of dividing the experience round by round, I am collectively sharing all the questions I was asked throughout the interview process.

Questions Asked

Core Java

• How does HashMap work internally?

• What happens when two keys have the same hash?

• Difference between fail-fast and fail-safe.

• Compile-time vs runtime polymorphism.

• Difference between method overloading and overriding.

• Runnable vs Callable.

Spring Boot and REST APIs

• Explain commonly used Spring Boot annotations.

• How does an API identify incoming data as the request body?

• What is the purpose of @RequestBody?

• Difference between @PostMapping and @PutMapping.

• Explain the Spring Bean lifecycle.

• What are the different Bean scopes?

Database

• How would you optimize a slow database query?

• What is indexing and how does it improve performance?

• Can adding too many indexes affect performance?

DSA

I was also asked Move Zeroes to the End of an Array.

For example: [0, 1, 0, 3, 12] => [1, 3, 12, 0, 0]

I solved it using a two-pointer approach in O(n) time and O(1) extra space, while maintaining the relative order of non-zero elements.