The following content is my own note from the book, "Designing Data-Intensive Applications". The writing is intended for people who want to dash through the book quickly.

Generally, data-intensive app require the following:

• database
• cache
• search index (search by keyword or filter)
• batch processing
• stream processing

To identify load parameters for scalability and performance, ask the following:

• request per second to a web server
• ratio of reads to writes in a database
• number of simultaneously active users (aka. peak time traffic)
• hit rate on a cache
• bottleneck dominated by a small number of extreme cases