ACS Group Software Engineer Interview Questions and Answers

Identify records in one table that do not match records in another using SQL queries.

• Use LEFT JOIN to find unmatched records: SELECT a.* FROM TableA a LEFT JOIN TableB b ON a.id = b.id WHERE b.id IS NULL.

• Use NOT EXISTS to filter unmatched records: SELECT * FROM TableA a WHERE NOT EXISTS (SELECT 1 FROM TableB b WHERE a.id = b.id).

• Use EXCEPT to find records in one table not in another: SELECT id FROM TableA EXCEPT SELECT...read more

Connection pooling is a technique of reusing database connections to improve performance.

• Connection pooling helps to reduce the overhead of creating and closing database connections.

• It maintains a pool of database connections that can be reused by multiple clients.

• It improves the scalability and performance of the application.

• Connection pooling can be configured with parameters like maximum pool size, timeout, etc.

• Exam...read more

SOLID principles are a set of five design principles for writing maintainable and scalable code.

• S - Single Responsibility Principle

• O - Open-Closed Principle

• L - Liskov Substitution Principle

• I - Interface Segregation Principle

• D - Dependency Inversion Principle

Generations of Garbage collection are used to manage memory in Java applications.

• Garbage collection is the process of automatically freeing up memory that is no longer in use by the application.

• Generational garbage collection divides objects into different generations based on their age and usage patterns.

• Young generation is where new objects are created and old objects that survive multiple garbage collections are mov...read more

IEnumerable is in-memory collection while IQueryable is a queryable data source.

• IEnumerable is used for querying data from in-memory collections like List, Array, etc.

• IQueryable is used for querying data from a database or remote data source.

• IQueryable supports deferred execution while IEnumerable does not.

• IQueryable allows for filtering, sorting, and paging to be done on the server side.

• IQueryable is more efficient wh...read more

IEnumerable is an interface while List is a class in C#.

• IEnumerable is read-only and can only be iterated over.

• List is a collection that can be modified and indexed.

• IEnumerable is more memory efficient for large datasets.

• List has more functionality like sorting and searching.

• IEnumerable can be used with LINQ queries.

• List is faster for small datasets.

API versioning is the process of managing and updating different versions of an API.

• API versioning allows developers to make changes to an API without breaking existing client applications.

• It involves assigning a version number to each release of the API.

• Versioning can be done through URL paths, headers, or query parameters.

• Examples of API versioning include Twitter API v1.1 and Google Maps API v3.

• API versioning is imp...read more

Prevent SQL Injection by using parameterized queries and input validation.

• Use parameterized queries instead of concatenating user input with SQL statements.

• Sanitize user input by validating and escaping special characters.

• Limit database user privileges to only necessary actions.

• Implement web application firewalls to detect and block SQL injection attempts.

• Regularly update and patch software to fix known vulnerabilities...read more

Delegates are reference types that hold a reference to a method. They are used to achieve loose coupling and extensibility.

• Delegates allow methods to be passed as parameters to other methods.

• They can be used to implement callbacks and event handlers.

• Delegates can be multicast, meaning they can hold references to multiple methods.

• There are two types of delegates: singlecast and multicast.

Multicasting in Angular is a technique to broadcast a single stream of data to multiple subscribers.

• It allows multiple subscribers to receive the same data stream.

• It reduces the number of HTTP requests made by the application.

• It can be achieved using RxJS operators like multicast() and refCount().

Observables are streams of data while Promises are one-time operations.

• Observables can emit multiple values over time while Promises can only resolve once.

• Observables can be cancelled while Promises cannot.

• Observables are lazy while Promises are eager.

• Observables can handle errors within the stream while Promises require a catch block.

• Observables are used in reactive programming while Promises are used in asynchronous ...read more

Base href in index.html is used to specify the base URL for all relative URLs in the document.

• Base href is used to set the base URL for all relative URLs in the document.

• It is helpful when working with multiple directories or when the website is hosted on a subdirectory.

• Example: <base href='https://www.example.com/'>

Polyfills are code that allows modern browsers to support features that are not natively supported.

• Polyfills are used to bridge the gap between modern web development and older browsers.

• They provide a way to use new features without worrying about browser compatibility.

• Polyfills can be used for features like CSS Grid, Fetch API, and ES6 syntax.

• They are often included in JavaScript libraries and frameworks like React an...read more

Life cycle hooks are methods that allow you to tap into the lifecycle of a component in Angular.

• Life cycle hooks are used to perform actions at specific stages of a component's lifecycle.

• There are eight different life cycle hooks in Angular.

• Examples of life cycle hooks include ngOnInit, ngOnChanges, and ngOnDestroy.

Component interaction is the process of communication and data exchange between different software components.

• Components can interact through APIs, events, or shared memory.

• APIs allow components to expose their functionality to other components.

• Events enable components to notify each other of changes or trigger actions.

• Shared memory allows components to access and modify the same data.

• Component interaction is crucial f...read more

Route guards are used in Angular to prevent unauthorized access to certain routes.

• Route guards can be used to check if a user is authenticated before allowing access to a route.

• There are three types of route guards: CanActivate, CanActivateChild, and CanLoad.

• CanActivate is used to protect individual routes, while CanActivateChild is used to protect child routes.

• CanLoad is used to prevent lazy-loaded modules from being ...read more

AOT stands for Ahead of Time compilation, a technique used to compile code before it is executed.

• AOT is used to improve the performance of applications by compiling code before it is executed.

• It is commonly used in mobile app development to reduce app startup time.

• AOT can also help to reduce the size of the application binary.

• Examples of AOT compilers include Google's Android Runtime (ART) and Apple's LLVM-based compil...read more

Two way binding is a technique used in software development to keep data synchronized between the model and the view.

• Two way binding allows changes made to the model to be reflected in the view and vice versa.

• It is commonly used in front-end frameworks like Angular and React.

• In Angular, two way binding is achieved using [(ngModel)] directive.

• In React, two way binding can be achieved using state and props.

• Two way bindin...read more