Use-cases of Stateless and Stateful Systems

Here are some common use cases for both stateless and stateful systems:

1. Use Cases for Stateless Systems

• Web APIs: Stateless systems are commonly used for building RESTful APIs. Each HTTP request contains all the information needed for the server to process it, allowing for easy scalability and distribution.
• Content Delivery Networks (CDNs): CDNs often use stateless caching servers to serve static content to users. Since each request is independent, caching servers can quickly retrieve and deliver cached content without the need for maintaining state.
• Serverless Computing: Serverless architectures rely on stateless functions that execute in response to events or triggers. Functions are stateless, short-lived, and scale automatically based on demand, making them well-suited for event-driven applications and microservices.
• Authentication and Authorization: Stateless authentication mechanisms, such as JSON Web Tokens (JWT), are commonly used to authenticate and authorize users in web applications. Tokens contain all necessary information, eliminating the need for server-side session management.
• Load Balancers: Statelessness is often a desirable trait for load balancers, as they can distribute incoming requests across multiple servers without maintaining session affinity or shared state.

2. Use Cases for Stateful Systems

• User Sessions: Stateful systems are commonly used to manage user sessions in web applications. Session data, such as user authentication details and shopping cart contents, is maintained on the server to provide continuity between user interactions.
• Databases: Stateful databases store and manage persistent data, ensuring consistency and durability across interactions. Examples include relational databases (e.g., MySQL, PostgreSQL) and NoSQL databases (e.g., MongoDB, Cassandra).
• Distributed Systems Coordination: Stateful components, such as distributed consensus algorithms (e.g., Raft, Paxos), are used to coordinate interactions between nodes in distributed systems. These components maintain state to ensure consistency and fault tolerance.
• Real-time Collaboration: Stateful systems are used in real-time collaboration applications, such as collaborative editing tools or messaging platforms. State is maintained to synchronize changes between multiple users and ensure data consistency.

In System Design, the choice between stateless and stateful architectures is pivotal. Stateless systems treat each request independently, offering scalability but sacrificing state persistence. Conversely, stateful systems retain client state, ensuring data integrity but complicating scalability. This article teaches the characteristics of these approaches, showing their impact on scalability, fault tolerance, and data management.