🧠 Client–Server Architecture

🔹 What it is:

Client–Server Architecture is a design model where two entities communicate —

• Client: the user or application that requests data or services.
• Server (Backend): the system that processes the request, performs necessary operations, and sends back the response.

⚙️ How it works (Flow):

1. Client → Backend:
   • The client sends a request (req) to the backend.
   • Example: A browser requesting user data from a web server.
2. Backend → Database:
   • The backend receives the request and may need data.
   • It then acts as a client itself to another service — typically a database.
   • Sends a request (req) to the database.
3. Database → Backend:
   • The database processes the query and sends back a response (res) containing the data.
4. Backend → Client:
   • The backend processes the data, formats it (e.g., JSON), and sends the response (res) to the client.

🔁 Key Points:

• The client never interacts directly with the database — all communication goes through the backend.
• The backend acts both as:
  • a server for the client, and
  • a client for other services (like databases, APIs, etc.).
• This structure improves security, scalability, and separation of concerns.

💡 Example: