Concepts in Distributed Systems

Performance Metrics of a Website:

• Response Time: The total time taken from the start of a request until the last piece of response data is received.
• Concurrency: The number of requests that the system can handle simultaneously.
• Concurrent Connections: The total number of TCP connections established by clients to the server. This refers to the total number of TCP connections per second.
• Request Count: Also known as QPS (Queries Per Second), it indicates how many requests are made per second.
• Concurrent Users: The number of users active within a unit of time.
• Throughput: The number of requests the system can handle in a unit of time.
• QPS: Queries Per Second, the number of queries per second.
• TPS: Transactions Per Second, the number of transactions per second.

A transaction refers to the process where a client sends a request to the server and the server responds. The timing starts when the client sends the request and ends when the server's response is received, allowing for the calculation of the time taken and the number of completed transactions.

A single visit to a page will generate one TPS; however, a single page request may result in multiple requests to the server, leading to multiple QPS.

Additional Characteristics of High-Performance Websites:

• High Performance: Provides a fast access experience.
• High Availability: The website service is always accessible.
• Scalability: Increases or decreases processing capacity through hardware adjustments.
• High Extensibility: Low coupling between systems, allowing for easy addition or removal of new features/modules.
• Security: Provides secure access to the website and data encryption, along with secure storage strategies.
• Agility: Responsive to changes and quick to adapt.