If you are asked to design a system to take user-provided URLs and transform them to shortened URLs, what would you do? How would you allocate the shorthand URLs? How would you implement the redirect servers? How would you store the click stats?

Lambda architecture = CQRS (batch layer + serving layer) + speed layer. It solves accuracy, latency, throughput problems of big data.

Using Lambda can address three issues brought by big data: accuracy (good); latency (fast); throughput (high). The lambda architecture can guide us on how to scale a data system.

Nonviolent Communication is not about appearing friendly, nor is it about getting others to do what we want; it concerns mutual understanding between people. There are two ways to strengthen connections and understanding between individuals: expressing our feelings and needs vulnerably; and actively listening to the feelings and needs of others.

KYC is not easy; employees outside the marketing department may never have the opportunity to understand buyers' needs. Buyer persona = buyer profile (who will buy) + buyer insights (when/how/why they buy)

The relational database is the default choice for most storage use cases, by reason of atomicity, consistency, isolation, and durability. How is consistency here different from the one in CAP theorem? Why do we need 3NF and DB proxy?

When customers evaluate a product or service, they weigh perceived value against actual price. The elements of value include functional value; emotional value; life-changing; and social impact.

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.