Meaning:
“流量” means “online traffic,” and “密码” literally means “password.” Because the amount of online traffic that a person or a topic can generate is a reflection of their popularity and may lead to sales revenue or advertisement income, online shopkeepers and celebrities make a lot of effort to attract online traffic. Effective tools and methods used to boost online traffic are therefore called “passwords to online traffic.”
Example:
A: 小林在小红书的账号最近涨粉涨得厉害。
Xiǎolín zài xiǎohóngshū de zhànghào zuìjìn zhǎngfěn zhǎng de lìhài。
Xiao Lin’s account on Xiaohongshu has recently gained a huge number of new followers.
B: 不知道他有什么流量密码。
Bù zhīdào tā yǒu shénme liúliàng mìmǎ。
I wonder what he did to boost online traffic.
A: 他图文连载了偶遇某明星的经过。
Tā túwén liánzǎi le ǒuyù mǒu míngxīng de jīngguò。
He posted a series of photos and texts about his experience when he ran into a showbiz celebrity.