100+ Lead Software Engineer Interview Questions and Answers

Pessimistic locking is when a resource is locked for a long time, while optimistic locking is when a resource is locked only when it is being modified.

• Pessimistic locking involves locking a resource for a long time to prevent other users from accessing it.

• Optimistic locking involves locking a resource only when it is being modified, allowing other users to access it in the meantime.

• Pessimistic locking is useful when conflicts are likely to occur, while optimistic locking is u...read more

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 pattern is used when we have a superclass with multiple subclasses and based on input, we need to return one of the subclass.

• It provides a way to delegate the instantiation logic to child classes.

• Example: java.util.Calendar, java.util.ResourceBundle, java.text.NumberFormat, etc.

Angular is a popular front-end web application framework that uses TypeScript as its primary language.

• Angular is developed and maintained by Google.

• It is used for building dynamic, single-page web applications.

• It uses TypeScript, a superset of JavaScript, which adds features like static typing and class-based object-oriented programming.

• Angular provides a range of features like data binding, dependency injection, and component-based architecture.

• Some popular websites built wi...read more

Static and default methods in functional interfaces provide utility methods and default implementations for interface methods in real-time applications.

• Static methods in functional interfaces can be used for utility methods that are not tied to a specific instance of the interface.

• Default methods in functional interfaces provide default implementations for interface methods, allowing for backward compatibility when new methods are added to the interface.

• In real-time applicati...read more

Use a bean before it is destroyed by implementing a pre-destroy method

• Implement a method annotated with @PreDestroy in the bean class

• This method will be called before the bean is destroyed

• Perform any necessary cleanup or final operations in this method

I am familiar with a variety of programming languages and tools.

• Languages: Java, Python, C++, JavaScript, SQL

• Tools: Git, JIRA, Jenkins, Eclipse, Visual Studio

• Frameworks: Spring, React, Angular, Node.js

• Databases: MySQL, MongoDB, Oracle

Load balancing is the process of distributing network traffic across multiple servers to avoid overloading a single server.

• Load balancing helps to improve the performance, availability, and scalability of applications.

• It can be achieved through hardware or software solutions.

• Examples of load balancing algorithms include round-robin, least connections, and IP hash.

• Load balancing can also be combined with other techniques such as caching and compression to further optimize perf...read more

Routing is the process of selecting a path for network traffic to travel from one network to another.

• Routing is done by routers in a network.

• Types of routing include static routing, dynamic routing, and default routing.

• Static routing involves manually configuring the routes.

• Dynamic routing uses protocols to automatically update the routing table.

• Default routing is used when there is no specific route for a packet.

• Examples of routing protocols include OSPF, BGP, and RIP.

Intermediate operators transform or filter the stream elements, while terminal operators produce a result or side effect.

• Intermediate operators include filter(), map(), sorted(), distinct(), etc.

• Terminal operators include forEach(), collect(), reduce(), count(), etc.

• Intermediate operators are lazy and do not execute until a terminal operator is called.

• Terminal operators trigger the stream processing and produce a result or side effect.

Answers to technical questions for Lead Software Engineer position

• Protractor is an end-to-end testing framework for AngularJS applications

• Package lock file is used to lock the version of dependencies installed in a project

• === checks for both value and type equality while == checks for value equality only

• function reverseNumber(num) { return parseInt(num.toString().split('').reverse().join('')) }

Condition can depend on various factors such as environment, genetics, lifestyle, and medical history.

• Condition can depend on environmental factors like pollution, climate, and access to healthcare.

• Genetics play a role in determining one's predisposition to certain conditions.

• Lifestyle choices such as diet, exercise, and stress management can impact one's overall health.

• Medical history, including past illnesses and treatments, can also influence current condition.

CORS (Cross-Origin Resource Sharing) is a security feature that restricts web pages from making requests to a different domain.

• CORS issue occurs when a web page tries to access resources from a different domain

• It is a security feature implemented by web browsers to prevent cross-site scripting attacks

• CORS issue can be resolved by configuring the server to allow cross-origin requests or by using JSONP

• It can occur in AJAX requests, web fonts, images, and videos

Aids patient will transfer faster than an asthma patient due to the nature of the diseases.

• Aids is a viral infection that can be transmitted through bodily fluids such as blood, while asthma is a chronic respiratory condition that is not contagious.

• Aids can be transmitted through unprotected sexual contact, sharing needles, or from mother to child during childbirth or breastfeeding.

• Asthma is a condition that causes inflammation and narrowing of the airways, leading to symptom...read more

A thread is a lightweight sub-process that allows concurrent execution within a process. Threads can be created in multiple ways.

• Threads can be created by extending the Thread class in Java.

• Threads can be created by implementing the Runnable interface in Java.

• Threads can be created using thread pools in Java.

• Threads can be created using asynchronous functions in JavaScript.

I prefer 5*5 as it is a standard mathematical operation for multiplication.

• Multiplication is a fundamental arithmetic operation.

• 5*5 is more commonly used in mathematical calculations.

• 5+5 is a simple addition operation.

Caching is the process of storing frequently accessed data in a temporary storage area for faster access.

• Caching reduces the time and resources required to access data.

• Types of caching include browser caching, server caching, and database caching.

• Browser caching stores web page resources like images, stylesheets, and scripts on the user's device.

• Server caching stores frequently accessed data on the server to reduce database queries.

• Database caching stores frequently accessed ...read more

Use the POJO's attributes that define equals() and hashCode() methods as the key in the Hashmap.

• Ensure the POJO class overrides equals() and hashCode() methods.

• Create an instance of the POJO and use it as the key in the Hashmap.

The best pen in the market should have a comfortable grip, smooth writing experience, long-lasting ink, and a stylish design.

• Comfortable grip for extended use

• Smooth writing experience for effortless writing

• Long-lasting ink to avoid frequent refills

• Stylish design to appeal to customers

Interfaces are contracts that define a set of methods that a class must implement. They help achieve abstraction and loose coupling.

• Interfaces provide a way to achieve abstraction and loose coupling in code.

• They define a set of methods that a class must implement, but not how they are implemented.

• Classes can implement multiple interfaces, allowing for greater flexibility and reusability.

• Interfaces are commonly used in dependency injection and mocking frameworks.

• Example: The J...read more

A View Model in Android is a class that stores and manages UI-related data in a lifecycle-conscious way.

• View Model helps to separate the UI data from the UI controller logic.

• It survives configuration changes and can be shared between fragments or activities.

• Example: ViewModel class in Android Architecture Components.

Web application is a complete software program accessed through a web browser, while web API application is a set of programming instructions that allow communication between different software systems.

• Web application is a complete software program accessed through a web browser

• Web API application is a set of programming instructions that allow communication between different software systems

• Web application provides a user interface for the end-user to interact with the softw...read more

Program to swap two numbers without using temp and encapsulation in Java with example

• Use XOR operator to swap two numbers without using temp variable

• Encapsulation is a mechanism to hide data and methods from outside world

• Example: private variables with public getter and setter methods

Sync call blocks the execution until the response is received, while asynchronous call allows the program to continue executing without waiting for the response.

• Sync call blocks the program execution until the response is received

• Asynchronous call allows the program to continue executing without waiting for the response

• Sync calls are easier to understand and debug, but can lead to performance issues if used excessively

• Asynchronous calls are more efficient for handling multipl...read more

CSV stands for comma-separated values, VP is validation protocol. 21CFR part 11 and EU annex 11 are regulations for electronic records and signatures in the US and EU. Gamp5 is a guideline for validation of computerized systems in the pharmaceutical industry.

• CSV is a file format used for storing tabular data in plain text, with each line representing a data record and each record separated by commas.

• VP is a validation protocol used to ensure that a system or process meets pre...read more

Encryption is the process of converting plain text into a coded message to prevent unauthorized access.

• Encryption uses an algorithm and a key to convert plain text into ciphertext.

• Decryption uses the same algorithm and key to convert ciphertext back into plain text.

• Common encryption algorithms include AES, RSA, and Blowfish.

• Encryption is used to protect sensitive data such as passwords, credit card numbers, and personal information.

• Encryption can be done at different levels s...read more

AIDL and HIDL are communication interfaces used in Android development. Android Boot Up Sequence, Architecture, Components Framework, and Activity Lifecycle are key concepts in Android development.

• AIDL (Android Interface Definition Language) is used for inter-process communication in Android. It allows different applications to communicate with each other.

• HIDL (Hardware Interface Definition Language) is used for communication between Android system services and hardware compo...read more

I prefer Java due to its platform independence, strong community support, and extensive libraries.

• Java is platform independent, allowing for greater flexibility in deployment.

• Java has a strong community support and a vast number of libraries available for various functionalities.

• Java is widely used in enterprise applications and has a proven track record of performance and scalability.

Implementing a real-time chat feature using WebSockets and Redis pub/sub

• Used WebSockets to establish a persistent connection between clients and server

• Utilized Redis pub/sub for broadcasting messages to multiple clients in real-time

• Implemented message queuing to handle high traffic and ensure message delivery

Fail safe focuses on ensuring system stability and preventing catastrophic failures, while fail fast prioritizes quick detection and response to errors.

• Fail safe is about designing systems to minimize the impact of failures and ensure stability.

• Fail fast is about quickly detecting and responding to errors to prevent further issues.

• Fail safe often involves redundancy and error checking mechanisms to prevent catastrophic failures.

• Fail fast encourages rapid feedback loops and ea...read more

Caching system improves performance by storing frequently accessed data in memory.

• Caching reduces the need to fetch data from the server, improving load times.

• Common caching systems include Redis, Memcached, and browser caching.

• Caching can be implemented at various levels such as browser, CDN, and server-side.

• Examples of cached data in frontend include images, CSS files, and API responses.

Design system is crucial for consistency, efficiency, and scalability in software development.

• Ensures consistency in UI/UX across products and platforms

• Promotes reusability of components and patterns

• Facilitates collaboration between design and development teams

• Increases efficiency by streamlining the design and development process

• Helps in scaling the product by providing a structured framework for growth

I communicate delays and requirements by providing clear updates, setting realistic expectations, and actively listening to feedback.

• Provide regular updates on progress and any delays that may impact timelines

• Clearly communicate any changes in requirements or scope

• Set realistic expectations for delivery timelines and potential challenges

• Actively listen to feedback and address any concerns or questions promptly

Check if two strings are anagrams of each other

• Create a character count array for both strings

• Compare the character count arrays

• If they are equal, the strings are anagrams

Print only values from a nested JS object

• Use Object.values() to get an array of values

• Recursively iterate through nested objects

• Filter out non-object values before iterating

Pure Components in React JS are components that do not re-render unless their props have changed.

• Pure Components extend React.Component and implement shouldComponentUpdate method for shallow comparison of props and state.

• Pure Components are more efficient than regular components as they prevent unnecessary re-renders.

• Example: class MyComponent extends React.PureComponent { // component code here }

React lifecycle methods include componentDidMount, componentDidUpdate, componentWillUnmount, etc.

• componentDidMount - called after component is rendered for the first time

• componentDidUpdate - called after component's state or props change

• componentWillUnmount - called before component is removed from the DOM

Breaking down a monolith into microservices involves identifying bounded contexts, decoupling components, and implementing communication mechanisms.

• Identify bounded contexts within the monolith to define the boundaries of microservices.

• Decouple components by extracting them into separate services with well-defined interfaces.

• Implement communication mechanisms such as RESTful APIs or message queues to enable interaction between microservices.

• Use containerization technologies l...read more

SSL is a security protocol used to establish an encrypted link between a web server and a browser.

• SSL stands for Secure Sockets Layer.

• It is used to protect sensitive information such as login credentials, credit card details, etc.

• SSL uses encryption to ensure that data transmitted between the server and browser cannot be intercepted by third parties.

• It is essential for e-commerce websites, online banking, and any website that handles sensitive information.

• SSL has been replace...read more

REST endpoints for a ticket booking system

• GET /events - get list of available events

• GET /events/{id} - get details of a specific event

• POST /events/{id}/tickets - book tickets for an event

• GET /bookings - get list of all bookings

• GET /bookings/{id} - get details of a specific booking

• PUT /bookings/{id} - update a booking

• DELETE /bookings/{id} - cancel a booking

CI/CD pipelines, frontend architecture, and e2e testing libraries are crucial aspects of software development.

• CI/CD pipelines automate the process of testing and deploying code changes, ensuring faster and more reliable software delivery.

• Architecting the frontend involves designing the structure, components, and interactions of the user interface to ensure scalability and maintainability.

• E2E testing libraries like Selenium or Cypress are used to simulate user interactions and...read more

Deploying service in production server involves building the application, configuring the server, and monitoring performance.

• Build the application code into a deployable package (e.g. JAR file for Java applications)

• Configure the production server with necessary dependencies and environment variables

• Deploy the application package to the server using tools like Docker, Kubernetes, or manual deployment scripts

• Monitor the performance of the deployed service using monitoring tools...read more