Understanding Backend Applications: A DevOps Engineer's Perspective

Understanding how backend applications work is crucial for DevOps and backend engineers. This article explains the process that occurs when a request is made to a backend application, the different components involved, and more.

Frontend vs. Backend

Every website or application consists of two main parts: the frontend and the backend.

• Frontend: This is what the user sees and interacts with. It's typically written in languages like HTML, CSS, and JavaScript.
• Backend: This handles all the application logic and data storage. It comprises a server hosting the application and a database.

As DevOps engineers, our focus is primarily on the backend. We are responsible for setting up servers, deploying applications, and managing databases.

Backend Components

A typical backend consists of:

• Server: Often hosted on a cloud provider like AWS, GCP, or Azure.
• Backend Application: Written in languages such as Python, Node.js, or Java.
• Backend Frameworks: Frameworks like Django (Python), Express (Node.js), or Spring Boot (Java) simplify application development.
• Package Managers: Used to manage dependencies and perform operations. For example, connecting to a PostgreSQL database or collecting OS information.
• Database: Stores user data. It can be a relational database (e.g., PostgreSQL, MySQL) or a NoSQL database (e.g., MongoDB, Cassandra).

Cloud vs. OnPremise

Creating servers and databases on the cloud is generally easier compared to onpremise solutions. Cloud providers offer managed services like Amazon RDS (for databases) and Amazon EC2 (for servers), streamlining the setup and management process.

The RequestResponse Cycle

Let's examine what happens when a user makes a request to a backend application:

1. A user (client) makes a request over the internet to the backend application.
2. The backend server receives the request and processes it.
3. The backend server sends back a response to the client.

This interaction is known as the requestresponse cycle. An API (Application Programming Interface) facilitates communication between the client and the server. Depending on the type of request, different API methods (e.g., GET, POST, PUT, DELETE) are used.

Status Codes

When a client makes a request, the server responds with a status code:

• 200 (OK): The request was successful.
• 400 (Bad Request): The request was invalid.
• 404 (Not Found): The requested resource was not found.
• 500 (Internal Server Error): An error occurred on the server.

Example: Amazon.com

Consider searching for "cat food" on Amazon.com:

1. Your browser sends a request to the Amazon server.
2. The Amazon server processes the request and retrieves the relevant data.
3. The Amazon server sends back the search results (cat food listings) to your browser.

This is a GET API call, and a successful response will typically have a 200 status code.

Scaling Your Application

If your application experiences high traffic, you can scale it by replicating the application across multiple servers. A load balancer distributes traffic across these servers, ensuring optimal performance. This, combined with autoscaling groups ensures that resources are dynamically scaled.

Additional Backend Tools

Other tools that might be found in a backend architecture include:

• Message Queues (e.g., RabbitMQ, Kafka): Used for asynchronous communication, such as sending emails.
• Monitoring Solutions (e.g., Prometheus, Grafana): Used to monitor application performance and identify issues.

Conclusion

Understanding the inner workings of backend applications is essential for DevOps engineers. This article provided a highlevel overview of the key components and processes involved in handling client requests and delivering responses.