How do microservices handle session persistence in distributed systems?

In a distributed microservices architecture, session persistence refers to the ability to maintain consistent user states (such as login information) across multiple requests, ensuring statelessness of services. Its importance lies in improving system scalability, reliability, and avoiding state coupling, making it suitable for scenarios requiring user session management such as e-commerce and social media.

The core principles include storing session states in external shared storage (e.g., Redis, databases), transmitting states via tokens (e.g., JWT), and handling routing through API gateways or load balancers. Features like state sharing and distributed consistency protocols enable horizontal scaling and fault tolerance. In practical applications, it enhances resilience, for example, reducing service dependencies through Redis clusters and improving overall availability.

Implementation steps: 1. Select external storage such as Redis to store session data; 2. Integrate token mechanisms to transmit states; 3. Configure load balancing to ensure consistency. Typical business values include enhancing the continuity of user experience, optimizing performance (e.g., reducing latency), and improving reliability under high concurrency.