Concepts

Account
An account is created upon successful registration with the cloud system. The account has full access permissions for all of its cloud services and resources. It can be used to reset user passwords and grant user permissions. The account is a payment entity and should not be used directly to perform routine management. For security purposes, create IAM users and grant them permissions for routine management.
User
An IAM user is created under an account to use cloud services. Each user has its own identity credentials (password and access keys).

The account name, username, and password will be required for API authentication.
Region
A region is a geographic area in which cloud resources are deployed. Availability zones (AZs) in the same region can communicate with each other over an intranet, while AZs in different regions are isolated from each other. By creating cloud resources in different regions, you can design applications to better meet customer requirements and comply with local laws and regulations.
AZ
An AZ comprises of one or multiple physical data centers equipped with independent ventilation, fire, water, and electricity facilities. Computing, network, storage, and other resources in an AZ are logically divided into multiple clusters. AZs within a region are interconnected using high-speed optical fibers to allow you to build cross-AZ high-availability systems.
Project
A project corresponds to a region. Default projects are defined to group and physically isolate resources (including compute, storage, and network resources) across regions. Users can be granted permissions in a default project to access all resources under their accounts in the region associated with the project. If you need more refined access control, create sub-projects under a default project and purchase resources in sub-projects. Then you can assign users the permissions required to access only the resources in the specific sub-projects.

Figure 1 Project isolation model
Checkpoint: When an application consumes data, the latest SN of the consumed data is recorded as a checkpoint. When the data is consumed again, the consumption can be continued based on this checkpoint.
APP: Multiple applications can access data in the same stream. Checkpoints generated for each application are used to record the consumed data in the stream by each application.