10+ Backend Software Developer Interview Questions and Answers

Design a scalable backend system to process user requests and send email results asynchronously.

• Use a message queue (e.g., RabbitMQ, Kafka) to handle user requests asynchronously.

• Implement a microservices architecture to separate processing tasks (e.g., data processing, email sending).

• Utilize cloud services (e.g., AWS Lambda, Azure Functions) for scalable processing without managing servers.

• Store results in a database (e.g., PostgreSQL, MongoDB) for retrieval and tracking.

• Use...read more

String pool is a cache of string literals in memory. Garbage collection frees up memory by removing unused objects.

• String pool is a part of heap memory where string literals are stored.

• Strings in the pool are shared among multiple objects to save memory.

• Garbage collection identifies and removes objects that are no longer in use.

• String pool can be accessed using the intern() method.

• String objects created using new keyword are not stored in the pool.

Rearrange an array of positive and negative numbers with positive numbers on the left and negative numbers on the right.

• Create two empty arrays, one for positive numbers and one for negative numbers

• Iterate through the original array and add positive numbers to the positive array and negative numbers to the negative array

• Concatenate the positive and negative arrays to create the rearranged array

Change binary tree so that parent node is the sum of root nodes

• Traverse the tree in post-order

• Update the parent node with the sum of its children

• Recursively update the parent nodes of the updated node

Synchronizing a HashMap ensures thread safety when multiple threads access it concurrently.

• Use Collections.synchronizedMap() to create a synchronized version of HashMap.

• Example: Map<String, String> syncMap = Collections.synchronizedMap(new HashMap<>());

• Manually synchronize blocks of code using synchronized keyword.

• Example: synchronized(syncMap) { syncMap.put(key, value); }

• Consider using ConcurrentHashMap for better performance in concurrent scenarios.

Printing matrix in spiral form and left+right view of tree

• For matrix, use four pointers to traverse in spiral form

• For tree, use recursion to traverse and print left and right view

• For left view, print the first node encountered in each level

• For right view, print the last node encountered in each level

Answering interview questions for software developer backend

• For School class, define properties like name, location, students, teachers, etc.

• For Instagram DB, define tables for users, posts, comments, likes, etc.

• Use relational database management system like MySQL or PostgreSQL.

• Implement proper indexing and normalization to optimize performance.

• Ensure data security and privacy by implementing authentication and authorization.

• Consider scalability and availability by using load...read more

Lazy loading is a technique used to defer the loading of non-critical resources until they are actually needed.

• It improves page load time and performance

• It reduces the initial load time of a web page

• It is commonly used for images, videos, and other media files

• It can be implemented using JavaScript or server-side programming

• Example: Images on a long-scrolling page are loaded only when they come into view

Yes, CICD stands for Continuous Integration and Continuous Deployment.

• CICD is a software development practice that involves continuous integration of code changes, automated testing, and continuous deployment of code to production.

• It helps in reducing the time between writing code and deploying it to production.

• Tools like Jenkins, Travis CI, and CircleCI are commonly used for implementing CICD.

• CICD also helps in detecting and fixing bugs early in the development cycle.

• It is a...read more