Amazon Software Developer interview questions often focus on coding skills, system design, data structures, algorithms, and problem-solving abilities. Below are 25 common questions with answers to help you prepare effectively for your Amazon interview.

Q1. What is the difference between a process and a thread?

A process is an independent program in execution with its own memory space, while a thread is a smaller unit within a process sharing the same memory.

Q2. Explain Big O notation.

Big O notation describes the upper bound of the time or space complexity of an algorithm, representing its worst-case performance.

Q3. What is a hash table and how does it work?

A hash table stores key-value pairs and uses a hash function to compute an index where the value is stored for fast access.

Q4. What are the different types of sorting algorithms?

Common types include Quick Sort, Merge Sort, Bubble Sort, Insertion Sort, Selection Sort, and Heap Sort.

Q5. Explain recursion with an example.

Recursion is a function calling itself to solve smaller instances of a problem. For example, calculating factorial: n! = n * (n-1)!

Q6. What is a binary search tree?

A binary search tree is a binary tree where the left child contains nodes with values less than the parent, and the right child contains values greater than the parent.

Q7. How do you handle collisions in a hash table?

Collisions can be handled using chaining (linked lists) or open addressing (probing).

Q8. What is multithreading and how is it useful?

Multithreading allows multiple threads to run concurrently within a program, improving performance and responsiveness.

Q9. Describe RESTful web services.

RESTful web services use HTTP requests to perform CRUD operations following REST architecture principles.

Q10. What are deadlocks and how can they be prevented?

Deadlocks occur when two or more threads are waiting indefinitely for resources held by each other. Prevention techniques include resource ordering and timeout.

Q11. Explain the difference between abstraction and encapsulation.

Abstraction hides complex implementation details from users, while encapsulation restricts access to certain components and bundles data with methods.

Q12. What is a linked list?

A linked list is a linear data structure where each element points to the next, allowing efficient insertion and deletion.

Q13. What is the difference between stack and queue?

A stack is Last-In-First-Out (LIFO) whereas a queue is First-In-First-Out (FIFO).

Q14. How do you design a scalable system?

By using load balancing, caching, database sharding, asynchronous processing, and designing stateless services.

Q15. What is a design pattern? Name a few.

Design patterns are reusable solutions to common software problems. Examples: Singleton, Factory, Observer, Strategy.

Q16. Explain the difference between synchronous and asynchronous programming.

Synchronous programming waits for a task to complete before moving on; asynchronous programming allows multiple tasks to run concurrently.

Q17. What is the difference between an interface and an abstract class?

Interfaces define method signatures without implementation; abstract classes can have implemented methods and can maintain state.

Q18. How do you optimize database queries?

By using indexes, avoiding unnecessary columns, limiting result sets, and using joins efficiently.

Q19. What is the difference between HTTP and HTTPS?

HTTPS is HTTP with encryption (SSL/TLS) to secure data transmission.

Q20. What are microservices?

Microservices are a software architecture style where applications are built as small, independent services that communicate over APIs.

Q21. What is continuous integration and continuous deployment (CI/CD)?

CI/CD automates the building, testing, and deployment of applications to improve software delivery speed and quality.

Q22. How do you manage memory in programming languages like Java?

Through garbage collection, which automatically frees memory allocated to objects that are no longer referenced.

Q23. What is a deadlock in multithreading?

Deadlock occurs when two or more threads are blocked forever waiting for resources held by each other.

Q24. What tools do you use for version control?

Common tools include Git, SVN, Mercurial, and Bitbucket.

Q25. How do you ensure code quality?

By writing unit tests, performing code reviews, using static analysis tools, and following coding standards.