Stateful

Describing a system, process, or object that retains information about its past interactions or operations, known as 'state'. This stored information allows the system to remember and respond differently based on prior events, providing context and enabling complex behavior. stateful systems are common in applications that need to manage sessions, track user data, or maintain persistent connections. The degree to which a system is 'stateful' can vary, depending on how much and how long its 'state' is preserved.

Stateful meaning with examples

• A web server handling user sessions is stateful. Each user's interactions (login, adding items to a cart, etc.) create and modify a session state stored on the server. Subsequent requests are linked to this session, allowing the server to personalize the user experience and remember their actions. Without session data, the server would be stateless. The website would not know who the user is, and not personalize the experience.
• A database connection is often stateful. After authentication, the connection maintains information like user permissions and the database server's status. Subsequent queries benefit from these established settings, enhancing efficiency and security. Closing the connection releases the state. Each query is only performed at the time it is run. The state can be held open to speed up additional requests.
• A network firewall is stateful; it inspects packets and records information about active network connections, like the source and destination IP addresses and ports. By tracking connection 'state', it can efficiently filter incoming and outgoing traffic, and allow traffic to be routed back to the source. This tracking allows the firewall to block malicious activity effectively and is also called connection tracking.
• A video game stores the 'state' of the game world, including player positions, inventory, and environmental conditions. Each action the player takes changes this state. If the player quits the game, the data can be saved for later play. If the player returns, it can be loaded, and the player can continue from where they left off, continuing the game and its state.