20+ Persistent Systems Lead Engineer Interview Questions and Answers

The default connection pooling in Spring Boot is HikariCP, which can be customized through properties in the application.properties file.

• HikariCP is the default connection pooling library in Spring Boot, known for its high performance and low overhead.

• To customize the connection pooling, you can modify properties like 'spring.datasource.hikari.*' in the application.properties file.

• For example, you can set maximum pool size, connection timeout, idle timeout, and other paramete...read more

Best practices for optimizing a Spring Boot application

• Use Spring Boot Actuator to monitor and manage application performance

• Implement caching mechanisms like Spring Cache to reduce database calls

• Optimize database queries and indexes for better performance

• Use asynchronous processing with Spring's @Async annotation for non-blocking operations

• Profile and analyze application performance using tools like VisualVM or JProfiler

A heap dump is a snapshot of the memory usage of a Java application at a specific point in time.

• Heap dumps can be generated using tools like jmap or VisualVM.

• They provide detailed information about objects in memory, their sizes, and references.

• Analyzing a heap dump can help identify memory leaks by pinpointing objects that are consuming excessive memory.

• Common signs of memory leaks in a heap dump include a large number of objects of the same type or objects that should have ...read more

Diagonally iterate through and print elements of a 2D array of strings.

• Use nested loops to iterate through rows and columns of the 2D array.

• Calculate the diagonal elements by incrementing row and column indices together.

• Print the elements as you iterate through the diagonal of the array.

Media query for 3 divs in row for desktop and column for mobile view

• Use min-width and max-width to target desktop and mobile views respectively

• Set display property to flex and flex-wrap to wrap for desktop view

• Set display property to block for mobile view

The Java Virtual Machine (JVM) is an abstract computing machine that enables a computer to run Java programs.

• JVM is platform-independent and converts Java bytecode into machine code.

• It consists of class loader, runtime data areas, execution engine, and native method interface.

• JVM memory is divided into method area, heap, stack, and PC register.

• Examples of JVM implementations include Oracle HotSpot, OpenJ9, and GraalVM.

Loops, map, and list are fundamental concepts in programming.

• Loops are used to repeat a block of code until a certain condition is met.

• Map is a higher-order function that applies a given function to each element of a list and returns a new list.

• List is a collection of elements that can be accessed by their index.

• Example: for loop, map function, list comprehension.

Exposure to the product can be validated through hands-on experience, user feedback, market research, and data analysis.

• Hands-on experience with the product through development and testing

• User feedback from customers or internal stakeholders

• Market research to understand the competitive landscape and user preferences

• Data analysis of usage metrics, customer behavior, and product performance

• Examples: Conducting user interviews, A/B testing features, analyzing sales data

Agile process involves iterative development, collaboration, and flexibility in responding to change.

• Agile process breaks down projects into smaller, manageable tasks called sprints.

• Teams work in short iterations, typically 2-4 weeks, to deliver working software.

• Regular meetings like daily stand-ups, sprint planning, and retrospectives help keep the team on track.

• Customer feedback is incorporated throughout the development process to ensure the final product meets their needs...read more

Customization tools and details are essential for tailoring engineering solutions to specific needs.

• Customization tools allow for adjusting parameters to meet unique requirements

• Details provide a deeper understanding of the system being engineered

• Examples include CAD software for designing custom parts and simulation tools for optimizing performance

Creating SQL queries for different scenarios

• Use SELECT statement to retrieve data from a table

• Use WHERE clause to filter data based on specific conditions

• Use JOIN clause to combine data from multiple tables

TSQL is a Microsoft proprietary extension of SQL used for querying and managing relational databases.

• TSQL stands for Transact-SQL and is used in Microsoft SQL Server.

• Optimization techniques in TSQL include indexing, query tuning, and avoiding unnecessary joins.

• Examples of optimization techniques in TSQL include using appropriate indexes on frequently queried columns and avoiding using functions in WHERE clauses.

A program to read data from excel.

• Use a library like Apache POI or OpenPyXL to read excel files.

• Identify the sheet and cell range to read data from.

• Parse the data and store it in a suitable data structure.

• Handle errors and exceptions that may occur during the process.

A basic trigger code is used to automatically perform an action when a certain event occurs in a database.

• Triggers are written in SQL and can be used to enforce business rules, perform data validation, or maintain data integrity.

• Example: CREATE TRIGGER trigger_name BEFORE INSERT ON table_name FOR EACH ROW BEGIN ... END;

REST and SOAP are web service protocols with different design principles

• REST (Representational State Transfer) is an architectural style that uses standard HTTP methods like GET, POST, PUT, DELETE for communication

• SOAP (Simple Object Access Protocol) is a protocol that uses XML for message exchange and can work over various transport protocols like HTTP, SMTP, etc.

• REST is lightweight, scalable, and easy to use, while SOAP is more rigid and has built-in security features

• REST i...read more

Automation framework is a set of guidelines, standards, and tools used for automating software testing.

• It provides a structured approach to automate tests

• It includes tools for test case management, test data management, and reporting

• It helps in reducing manual effort and increasing test coverage

• Examples include Selenium, Appium, and TestNG

let is block scoped, const is constant, var is function scoped

• let: block scoped, can be reassigned

• const: block scoped, cannot be reassigned, but its properties can be modified

• var: function scoped, can be reassigned

Spring is a lightweight framework that provides comprehensive infrastructure support for developing Java applications.

• Spring works internally by using Inversion of Control (IoC) container to manage Java objects.

• It uses Dependency Injection to inject the dependencies of an object at runtime.

• Spring also provides Aspect-Oriented Programming (AOP) support for cross-cutting concerns.

• It utilizes various modules like Core, Context, AOP, JDBC, ORM, etc., to provide different function...read more

A program to reverse a string

• Iterate through the string from end to start and append each character to a new string

• Use built-in functions like reverse() or StringBuilder.reverse() in some programming languages

• Convert the string to an array, reverse the array, and then convert it back to a string

Optimization techniques for React include code splitting, lazy loading, memoization, and virtualization.

• Code splitting: Break down the code into smaller chunks to load only what is necessary for each page.

• Lazy loading: Load components only when they are needed, improving initial load time.

• Memoization: Cache the results of expensive function calls to avoid redundant calculations.

• Virtualization: Render only the visible elements in a list, improving performance for large dataset...read more

Databricks is built on Apache Spark, a unified analytics engine for big data processing.

• Databricks is built on top of Apache Spark, which provides a unified analytics engine for big data processing.

• It offers a collaborative platform for data scientists, data engineers, and business analysts to work together.

• Databricks provides tools for data ingestion, data processing, machine learning, and visualization.

• It supports multiple programming languages like Python, Scala, SQL, and ...read more

Check if a string is a palindrome in Python

• Use string slicing to reverse the string and compare with the original string

• Remove spaces and convert to lowercase for accurate comparison

• Use a for loop to iterate through the string and check if it is a palindrome