Tell me more about horizontal scaling. What types are there?

Horizontal scaling (scale-out) is a method of increasing system performance by adding more identical nodes (servers, containers, etc.) that operate in parallel. Unlike vertical scaling (scale-up), where resources of a single node (CPU, RAM) are increased, horizontal scaling enhances the overall system throughput.

Main types of horizontal scaling:

1. Load Balancing

   • Adding new servers behind a load balancer.
   • The load balancer distributes requests evenly or according to specified rules.

2. Data Sharding/Partitioning

   • Dividing data into parts (shards), each served by a separate node.
   • Allows processing more data and requests in parallel.

3. Functional Scaling (Microservices)

   • Dividing the application into independent services that can be scaled separately.

4. Geographical Scaling

   • Placing nodes in different geographic regions to reduce latency and increase fault tolerance.

Horizontal scaling requires a well-thought-out architecture to ensure data consistency, load balancing, and fault tolerance.