When reading data from a hard disk, a database join operation is time-consuming and 99% of the time is spent on disk seek. To optimize read performance, denormalization is introduced and four categories of NoSQL are here to help.

To better sell products, you need to know your customers better. A generic buyer profile doesn’t help in knowing his buying decision. The most effective way to build buyer personas is to interview buyers who have weighed their options but finally made the decision you expect.

What are CAC, LTV, and PBP in marketing? CAC (Customer Acquisition Cost), LTV (Customer Lifetime Value), PBP (Payback Period). The LTV:CAC ratio helps you determine how much you should spend to acquire a customer for sustainable growth.

Judgments and violence are tragic expressions of unmet needs. Nonviolent communication can improve communication quality by valuing everyone’s needs. It is NOT about being nice or making others do what we want.

A bloom filter is a data structure used to detect whether an element is in a set in a time and space efficient way. A query returns either "possibly in set" or "definitely not in set".

A skip-list is essentially a linked list that allows you to do a binary search on. The way it accomplishes this is by adding extra nodes that will enable you to ‘skip’ sections of the linked-list. There are LevelDB MemTable, Redis SortedSet and Lucene inverted index using this.

A skip list is essentially a linked list that allows for binary search. It achieves this by adding extra nodes that enable you to "skip" parts of the linked list. Given a random number generator to create these extra nodes, a skip list has O(log n) complexity for search, insert, and delete operations.

A Bloom filter is a data structure that is used to determine whether an element is a member of a set with a much higher space and time efficiency than other general algorithms. The results obtained using a Bloom filter may yield false positive matches, but cannot yield false negative matches. Elements can be added to the set, but cannot be removed; the more elements added to the set, the greater the likelihood of false positives.

Customer Acquisition Cost is the cost to convert a customer to buy a product/service. Lifetime Value is the estimated net profit we can make from a customer. Payback Period refers to the period of time required to recoup the funds expended in an investment.

An economic moat refers to a company's ability to maintain a competitive advantage over its rivals, protecting long-term profits and market share. Elements that do not constitute an economic moat include: technology; extensive reading; master's degrees or other degrees from top universities; experience. Elements that constitute an economic moat include: economies of scale and scope; network effects; intellectual property; high customer switching costs.