A valid key should follow these rules:

• A name with an optional prefix, separated by a slash.
• A prefix must be a DNS subdomain, separated by dots, no longer than 253 characters.
• A name must be less than 63 characters with the combination of [a-z0-9A-Z] and dashes, underscores, and dots. Note that symbols are illegal if put at the beginning and the end.

A valid value should follow the following rules:

• A name must be less than 63 characters with the combination of [a-z0-9A-Z] and dashes, underscores, and dots. Note that symbols are illegal if put at the beginning and the end.

You should also consider the purpose, too. For example, there are two projects, pilot and poc. Also, those projects are under different environments, such as develop and production. In addition, some contain multiple tiers, such as frontend, cache, and backend. We can make our labels key and value pair combination like follows:

  labels:
    project: pilot
    environment: develop
    tier: frontend