System Design 1 - Basic request flow

Understanding Request Flow in System Design

we'll dive into how a request flows through a system from the frontend to the backend (assume net banking).

Here’s an illustration to help us visualize the process.

👤 Step 1: User Interaction

• A user initiates a request by interacting with the frontend application (e.g., clicking a button, submitting a form).

🌐 Step 2: DNS Lookup

• The request is sent to the DNS server to resolve the domain name (e.g., www.netbanking.hdfc.com) into an IP address, directing the request to the correct server.

  Detailed Explanation:

  • What is DNS?: DNS stands for Domain Name System. It translates human-readable domain names into IP addresses that computers use to identify each other on the network.

  • How it works:

    • When a user enters a URL into their browser, the browser sends a DNS query to a DNS server.

    • The DNS server looks up the domain name in its database. If it doesn’t have the record, it queries other DNS servers in a hierarchical manner until it finds the IP address.

    • Once the IP address is found, it is sent back to the user's browser.

    • The browser can now send the HTTP request directly to the IP address of the server hosting the website.

Example:

• User types "www.netbaking.hdfc.com" in their browser.

• Browser sends a DNS query to the DNS resolver.

• The DNS resolver checks its cache. If not found, it queries other DNS servers.

• Eventually, the IP address (e.g., 192.0.2.1) is found and returned to the browser.

• The browser uses this IP address to send a request to the correct server.

This process ensures that users can access websites using easy-to-remember domain names instead of numeric IP addresses.

🖥️ Step 3: Application Server

• The resolved request reaches the application server, which handles the business logic and processes the request.

🔀 Step 4: Message Queue & Data Storage

• The application server sends the request to a message queue for asynchronous processing.

• It also interacts with the data storage to retrieve or store data as needed.

🗄️ Step 5: Processing & Storage

• The data storage layer retrieves necessary information and updates records if required.

• The message queue ensures tasks are handled efficiently without blocking the main process.

↩️ Step 6: Response to User

• Finally, the application server sends a processed response back to the user, completing the request cycle.

📈 Understanding this flow is crucial for designing scalable and efficient systems. Each component plays a vital role in ensuring smooth operation and quick response times.