Can you list and describe the most popular design patterns used in building microservice systems?

Microservice systems often employ the following design patterns:

• API Gateway — a single entry point for all clients that routes requests to the appropriate microservices, provides authentication, data aggregation, and caching.

• Circuit Breaker — prevents cascading failures by disabling calls to non-operational services and giving them time to recover.

• Service Discovery — allows microservices to automatically find each other in a dynamic environment, for example, through a service registry.

• CQRS (Command Query Responsibility Segregation) — separates read and write operations to optimize performance and scalability.

• Event Sourcing — stores the system state as a sequence of events, facilitating recovery and auditing.

• Saga — manages distributed transactions through a sequence of local transactions with compensating actions.

• Sidecar — isolates auxiliary functions (logging, monitoring, security) into a separate process running alongside the main service.

These patterns help solve common problems of distributed systems, increase fault tolerance, and simplify scaling.