Ce microservicii pot fi scalate orizontal?

Practically any microservice designed according to the principles of stateless (without maintaining state).

Main criteria:

• Stateless (without storing intermediate state): The service does not store information specific to a particular request between calls. All necessary data is either transmitted with the request or stored in an external, scalable source (database, cache, message broker).
• Deterministic behavior: With the same input data, the service always produces the same result, regardless of which instance (server) it runs on.
• Independence: The service is not tightly bound to a specific machine or resource that cannot be easily replicated.

Examples of microservices that scale well horizontally:

• Authentication and authorization services.
• Services processing HTTP requests (API Gateways, backend services).
• Services processing messages from queues.
• Services for executing background tasks (worker services).
• Services for report generation (if data is taken from an external database).

Stateful microservices scale horizontally with more difficulty and require special approaches, such as:

• Partitioning (Partitioning/Sharding): Dividing data among service instances.
• Distributed databases: Using database systems that ensure scalability and replication.
• Using In-Memory Data Grids: For caching and processing state in distributed environments.

It is important to understand that even stateless services require scalable infrastructure for data storage (database, cache, message broker) and orchestration (Kubernetes, Docker Swarm) for effective horizontal scaling.