We are going to explore in his entry, Stateful vs Stateless in Architecture, the importance of choosing between two ways of building services and applications, especially when creating a new software architecture.

In an increasingly microservices-oriented world, it is crucial to understand and differentiate between Stateful and Stateless. In other words, services with state or without state, as the choice of characteristics and resources will depend on the application or service.

Let’s start with some theory and definitions about Stateful and Stateless.

Stateful Vs Stateless

The main and clearest difference between Stateful and Stateless is that the latter does not depend on a persistent storage system, whereas Stateful requires some form of persistent storage. For example, MongoDB is considered Stateful because it needs a place to store information persistently.

Generally, when working in a world of microservices and containers, it is common to start with stateless applications, meaning without state. This helps in adapting more easily to such architectures and allows for breaking down and migrating a monolith more easily, as well as enabling independent scaling.

Key characteristics of Stateless applications

• Stateless applications or services perform a single function.
• In this type of architecture or service, the server relies solely on the request made with each call, without considering previous information or requests. In other words, the server does not need information about the state of other requests.
• Since they have no state, different requests can be handled by different servers.
• Any instance can perform any task, which increases resilience and elasticity in this type of stateless service.
• Generally, this design of services or applications is closely linked to microservices and container architectures.
• An architecture based on Orchestration with stateless applications determines the best location for running containers in terms of resources and high availability. It allows for implementing failover measures.

Main characteristics of Stateful applications

• Typical Stateful applications are often databases.
• They are usually involved in transactions and stateful applications, such as banking applications.
• The server processes requests based on previous requests, meaning the server can process and maintain the state with each request.
• In an architecture with Stateful applications, the state information must be shared with all servers or services that need it or use the same server to process all requests related to the same state information.
• In the world of microservices architecture, one of the patterns for Stateful applications is Orchestration, which allows managing high availability of services. In this microservices architecture pattern, Stateful applications also help determine the best location for executing containers from a storage and network perspective.

Key differences between Stateful vs Stateless in Architecture

Let’s now enumerate the main characteristics of stateless and stateful applications:

1. States: Stateful applications react based on the current state, whereas stateless applications are independent of the state and previous or subsequent requests.
2. Information storage: Stateful applications store and use information, often to identify the user making the request, ensuring persistent connection. On the other hand, when the server doesn’t store data but connects to a database to verify what is needed, it is considered stateless.
3. Requests: All requests made in stateless services contain all the necessary information and follow a request-response cycle. In contrast, in stateful applications, requests depend on the server’s state.
4. Generated state: We generate and store a session on the server when creating stateful applications.
5. State in the client: Stateless applications are created when we send requests to obtain certain information and make subsequent requests based on that information, storing everything in the client.
6. Use cases: In a microservices architecture with containers, developers most commonly use stateless applications or services.. In contrast, stateful applications are more common in monolithic architectures

Benefits of Stateless applications

Next, we will list some benefits of using Stateless, for example in a microservices architecture:

1. Easy creation and addition of new instances.
2. Maintains consistency across multiple services or applications.
3. Allows for easier maintenance and error detection as they are generally smaller applications.
4. Eliminates the problems or efforts of creating user sessions.
5. Allows for easy scalability of applications.
6. Typically requires less server memory and resource usage.
7. Avoids problems related to session expiration since there are no sessions or state to manage.
8. Stateful applications or services can cause issues when making requests from different browsers, while stateless applications facilitate navigation.

Conclusion:

In a world increasingly focused on microservices and containers, it is crucial to establish a strong foundation from the beginning. That is why in this entry, “Stateful vs Stateless in Architecture,” we aim to explain the differences between these two types of services or applications.