Now, let's move on to 1.b Why is System Design Important?

System design is important for several key reasons, all of which become increasingly critical as systems grow in size and complexity. These reasons are centered around the core non-functional requirements of a system:

• Scalability: This is the ability of a system to handle a growing amount of work, either by adding resources to the existing system (vertical scaling) or by adding more systems (horizontal scaling). A well-designed system can scale gracefully without requiring major re-architecting. For example, if a social media platform expects a 10x increase in users over the next year, the system design must accommodate that growth. Without good design, the system might become slow, unresponsive, or even crash under increased load.

• Reliability: This refers to the probability that a system will function correctly for a specified period. A reliable system is one that consistently produces the correct output and doesn't experience frequent failures. System design plays a crucial role in ensuring reliability through techniques like redundancy, fault tolerance, and rigorous testing.

• Availability: This is the proportion of time that a system is operational and accessible to users. High availability is crucial for many applications, especially those that provide critical services. System design addresses availability through techniques like load balancing, failover mechanisms, and geographically distributed deployments. A system that's down frequently is useless, even if it's perfectly reliable when it is up.

• Maintainability: This is the ease with which a system can be modified, updated, and fixed. A well-designed system is modular, well-documented, and easy to understand. This reduces the cost and effort required to make changes and add new features over time. Poorly designed systems become "legacy code" very quickly, making them difficult and expensive to maintain.

• Fault Tolerance: This is the ability of a system to continue operating correctly in the event of failures. No system is perfect, and components will fail. A fault-tolerant system is designed to handle these failures gracefully, without causing a complete system outage. This might involve having backup systems, automatic failover, or mechanisms to isolate and recover from failures.

• Performance: Although we mentioned scalability which deal with handling increased workload. Performance is how fast a system is at any point. System design will consider the technologies, techniques to deliver maximum performance at any given load.

In summary: System design is the foundation upon which large, successful software systems are built. It's the difference between a system that can handle the demands of a growing user base and a system that collapses under its own weight. It directly impacts the user experience, the cost of development and maintenance, and the overall success of the project. For an L5 interview at Google, demonstrating a strong understanding of these principles is absolutely essential.