Server side and client side processing A-level Computer science (OCR) 1.3.4 (d)

What is client side processing, what languages are used and for what purposes?

Client side processing:

• Client-side processing operations are executed directly on the user's device, typically within their web browser.

Languages and purposes:

• Languages like JavaScript, HTML, and CSS are used for tasks such as validating user input, updating the UI dynamically, and creating interactive elements.

What is server side processing, what languages are used and for what purposes?

Server side processing:

• Server side processing refers to operations that are carried out on a remote server.

• Results are sent back to the users browser.

Languages and their purposes:

• Languages like PHP, Python and Node.js are most commonly used.

• These tasks include database queries, user authentication and complex business logic.

What are the advantages of client side processing?

Responsiveness:

• Improved responsiveness since the processing occurs on the users device.

Less server load:

• Reduced server load as the processing was occurs only the users device.

Efficiency:

• Real time interactions and instant feedback without needing to reload the page.

What are the disadvantages of client side processing?

Visible code:

• Security risks as the code is visible and can be manipulated by the user.

Performance in relation to device:

• Dependent on the users device and browser which may cause variations in performance.

Limited server resources:

• Limited access to server resources such as databases and files.

What are the advantages of server side processing?

Hidden code and data:

• More secure as the code and sensitive data are processed on the server away from the user.

Access to server resources:

• Full access to sever resources such as databases, files and API’s.

Consistent performance:

• Consistent performance across all devices since the server handles processing.

What are the disadvantages of server side processing?

Need for constant communication:

• Slower user experience due to constant need for communication between the server and the client.

Server load (multiple user requests):

• Higher server load as it needs to process multiple user requests.

Latency for processes requiring user response:

• Increased latency for user interactions that require a response from the user.

Explain how JavaScript is used in client side processing.

Realtime/ dynamic changes:

• JavaScript allows for real time interactivity and dynamic changes on a webpage without reloading the entire page.

Validation, UI and realtime data updates:

• It can be used for tasks like validation, updating the user interface (e.g showing/ hiding elements),and handling AJAX requests to perform realtime data updates.

Name three common languages used for client side processing.

• JavaScript

• HTML

• CSS

Name three common languages used for server side processing.

• SQL

• PHP

• Python

What is form validation and how can it be handled differently using server side and client side.

Form validation:

• Form validation ensures that the user input follows a specific set of rules before it is submitted.

Client side:

• Client side validation (using JavaScript), checks the data instantly within the browser providing instant feedback.

Server side:

• server side validation occurs after the data is sent to the server, ensuring inputs are secure and meet necessary requirements (especially important for security).

Explain how AJAX is used to improve the user experience in client server interactions.

AJAX:

• AJAX (Asynchronous JavaScript and XML), allows the client (browser) to send and receive data from the server asynchronously, without requiring the entire page to reload.

Improves user experience:

• This improves responsiveness and creates a smoother user experience, such as real time updates in search results or dynamically loading more content.

In a web application where a user is filling out a form, what are the security risks if only client side validation is used, and how can server side validation mitigate these risks?

Risks (client side):

• Client side validation can only be bypassed by users manipulating the JavaScript or submitting malicious data directly to the server.

Resolution (server side):

• Server side validation mitigates this by ensuring the data meets the necessary security standards (e.g length, format, escaping special characters) after it has been sent to the server, preventing attacks like SQL injection.

What is the difference between client side rendering and server side rendering.

Client side:

• Client side rendering refers to the generating of content of a webpage in the user’s browser using JavaScript.

• This is common in single page applications (SPA’s) where only parts of the page are updated without reloading the entire page.

Server side:

• Server side rendering generates the complete HTML page on the server and sends it to the client.

• This approach ensures that content is immediately visible when the page loads.

How might the choice difference between client side processing and server side processing affect the scalability of a web application with millions of users?

Reduce in server load:

• Client side processing reduces server load because many tasks are offloaded to the users device.

Scalability:

• This allows for better scalability since the server is less overwhelmed with processing.

Central work load, limited scalability:

• However server side processing centralises the workload, which may limit scalability.

Increased resource demands:

• More users result in increased server resource demands, and the server might struggle to handle the load, especially if processing-intensive tasks like database queries are involved.

Why is server side processing necessary for handling user authentication.

Handles sensitive info securely:

• Server side processing is required for user authentication because it securely handles sensitive information such as usernames and passwords.

Can hash passwords:

• The server can hash passwords and validate credentials against a database and create secure sessions or tokens.

Client side is insufficient:

• client side processing alone cannot ensure secure storage or transmission of sensitive data.

What are rich user interfaces and how are they achieved through client side processing?

Rich user interface:

• Rich user it interfaces are dynamic interactive webpages that provide a smooth and engaging user experience.

How are they achieved?

• They are achieved through client side processing using technologies like JavaScript CSS and HTML to create animations real time updates and interactive features such as sliders drag and drop elements and tool tips often without needing to reload the page.

A social media platform uses AJAX to update user posts in real time.

Describe the interaction between client side and server side processing in this scenario and how the platform ensures security and performance.

Client side:

• JavaScript using Ajax requests new posts from the server at regular intervals or when the user scrolls down.

• This allows the user interface to be updated dynamically without reloading the page.

Server side:

• The server handles database queries to retrieve the latest posts and sends this data to the client in a format like JSON.

• The server must also verify that the user has permission to see the posts process requests efficiently and prevent excessive resource usage.

Security:

• Security: to ensure security the server validate each request check user authentication and users HTTPS do you protect data in transit. cross site scripting (XSS) and SQL injection are mitigated through proper input validation and sanitisation.

What are cookies and how do they facilitate client/server communication.

Cookies:

• Cookies are small pieces of data stored by the browser on the client side.

Use:

• They are often used to remember user preferences or maintain session state between the client and server.

• When the browser makes a request to the server the cookie data is sent along with it allowing the server to recognise the user or maintain continuity in their reaction.

Compare the security implications of handling user payments using client side processing versus server side processing in an e-commerce platform.

Client side:

• Sensitive payment information like credit card details should never be handled solely on the client side because it can be intercepted manipulated or viewed by users.

• Client side processing might only handle simple form validation or UI feedback.

Server side:

• Secure processing of payments must be done server side, the server encrypts sensitive data processes transactions through secure payment gateways and ensures that credit card details are not exposed to unauthorised parties.

• This approach complies with regulations like PCI DSS for handling financial data securely.

How does caching improve the performance of server side processing in web applications?

Stores frequently requested data:

• Cashing stores frequently requested data like database queries or webpages in temporary storage.

Reduces server load:

• This reduces the need to repeatedly process the same request improving performance by lowering response times and reducing server load.

What is the role of a database in server side processing and why can’t it be accessed directly through client side code.

Storage of large amounts of info:

• Databases store large amounts of structured data for example user information and posts.

Server side to ensure security and efficiency:

• They are managed server side to ensure security, data integrity and efficient querying.

Client side:

• Direct access to a database from client side code would expose sensitive data and post significant security risks such as data theft or manipulation.