More Mega Store Interview Questions and Answers

Exception handling is crucial in programming to handle errors and ensure proper execution. The 'finally' block is used to clean up resources, and throwing exceptions allows for error propagation.

• Exception handling is used to manage errors and unexpected situations in a program.

• The 'finally' block is used to execute code that should always run, regardless of whether an exception is thrown or not.

• Throwing exceptions allo...read more

ACID properties ensure data integrity in transactions. CAP Theorem states that a distributed system can only guarantee two out of three: Consistency, Availability, Partition Tolerance.

• ACID properties: Atomicity, Consistency, Isolation, Durability

• Example: In a banking application, a transfer of funds should be atomic, consistent, isolated, and durable

• CAP Theorem: Consistency, Availability, Partition Tolerance - a distri...read more

Comparable is an interface used for natural ordering, while Comparator is used for custom ordering in Java Collections.

• Comparable interface is used to define the natural ordering of objects. It is implemented by the class whose objects are to be sorted.

• Comparator interface is used to define custom ordering of objects. It is implemented by a separate class.

• To implement Comparable, the class needs to override the compare...read more

Generics in Java allow for creating classes, interfaces, and methods that operate on types parameterized at compile time.

• Generics provide type safety by allowing compile-time type checking.

• They enable code reusability and reduce the need for casting.

• Example: List<String> list = new ArrayList<>();

Code to reverse a string using recursion

• Create a recursive function that takes a string as input

• Base case: if the string is empty or has only one character, return the string

• Recursive case: return the last character of the string concatenated with the result of calling the function on the substring excluding the last character

Object comparison with specific fields involves comparing values of selected fields between two objects.

• Object comparison can be done by comparing the values of specific fields in two objects.

• Fields can be selected based on unique identifiers or criteria for comparison.

• Example: Comparing the 'name' field of two person objects to check if they are the same.

Distributed transactions in microservices involve using compensating transactions and event-driven architecture.

• Microservices typically use compensating transactions to maintain consistency across multiple services.

• Event-driven architecture can help in coordinating distributed transactions by using events to trigger actions in different services.

• Implementing distributed transactions in microservices requires careful de...read more

Aggregator pattern is used in microservices architecture to combine multiple service responses into a single response.

• Aggregator pattern helps in reducing the number of client requests by combining multiple service responses.

• It can be implemented using a separate service or within an existing service.

• Example: A shopping website aggregating product information from different microservices like inventory, pricing, and re

Factory design pattern is a creational pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

• Factory method pattern defines an interface for creating objects, but lets subclasses decide which class to instantiate.

• It promotes loose coupling by eliminating the need to bind application-specific classes into the code.

• Example: A car m...read more

Indexing in a database is a technique to improve the speed of data retrieval by creating a data structure that allows for quick lookup.

• Indexing involves creating a separate data structure that contains pointers to the actual data in the database.

• Common data structures used for indexing include B-trees, hash tables, and binary search trees.

• Indexes can be created on one or multiple columns in a database table to speed up...read more

My approach involves using load balancing, caching, asynchronous processing, and horizontal scaling.

• Implement load balancing to distribute requests evenly across multiple servers.

• Utilize caching mechanisms to store frequently accessed data and reduce response times.

• Use asynchronous processing for long-running tasks to free up resources for handling more requests.

• Implement horizontal scaling by adding more servers to ha...read more

CQRS pattern in microservices separates read and write operations for improved scalability and performance.

• CQRS stands for Command Query Responsibility Segregation

• It separates the read and write operations into two different models

• Write operations update the data store, while read operations query a separate data store

• CQRS can improve performance and scalability by allowing each model to be optimized for its specific t

API Gateway acts as a single entry point for all client requests in a microservices architecture.

• API Gateway handles authentication, authorization, rate limiting, and routing of requests to appropriate microservices.

• It helps in decoupling client applications from individual microservices, providing a more flexible and scalable architecture.

• API Gateway can also perform tasks like request/response transformation, logging...read more

SQL query to fetch data from two tables using joins

• Use the JOIN keyword to combine rows from two tables based on a related column

• Specify the columns to select from each table in the SELECT statement

• Use the ON keyword to specify the join condition