[System Design] Scaling methodologies

Wikipedia says, Scalability is the property of a system to handle a growing amount of work by adding resources to the system. With increase in customer demand, Servers hit the scale problems. There are 2 standard ways of handling the Scalability.
1. Horizon Scaling: Add more servers/Machines when there is a increase in load.

• Demands load balancing to balance client requests.
• Results in distributed systems and possible data inconsistency.

2. Vertical Scaling: Add more resources to the same server.

• Single server holds all the data and hence there will be no data consistency issues.
• Will result in better IPC as things are local to single server.
• Can result in Single Point of failure.
• Cannot go beyond certain hardware limits.

In practical, it is better to use a combination of both to achieve better results. Perform the Vertical scaling and move to Horizontal scaling after some peek limits.