A Stateful Application is a type of application that maintains client session data or "state" across multiple interactions or requests. In other words, stateful applications retain information about a user’s activity or session history, allowing for a more personalized, consistent experience throughout their interaction with the application. Stateful applications are common in scenarios where user-specific data is essential, such as shopping carts, online banking, and gaming applications.

Stateful applications require dedicated resources to track sessions, which can include:

Session Persistence: Stateful applications use session identifiers to keep track of each user’s interactions over time, such as items added to a cart or user-specific preferences.
Data Storage and Synchronization: They typically use databases or storage systems to manage and sync session data, ensuring continuity even if the user’s connection is interrupted.
Resource Management: Stateful applications often require more server resources to manage session states, making horizontal scaling challenging without robust load balancing.
While stateful applications offer rich, customized experiences, they are more complex to scale compared to stateless applications. Managing state requires careful consideration of resources, data synchronization, and availability, which often necessitates additional layers of infrastructure to handle session data across distributed systems.