The high availability of the system needs to consider: the high availability of its own services, the impact of upstream and downstream services.
Your own services need to be monitored, pressure tested, downgraded, denial of service, and flexible to control the reasonable use of resources, such as CPU, memory, disk, network, and threads. Once a certain resource exceeds the load, online problems are prone to occur. Perform service redundancy, remote disaster recovery, cluster deployment, and load balancing.
Do a good job of monitoring and limiting upstream services, and make plans for retrying, fuse downgrading, and bottoming out for downstream services.
There is also high availability of data storage, data master-slave replication, data master-slave switching, and data fragmentation (sub-database and table).
Reference:
How to ensure the stability and high availability of a highly concurrent system
! An article to understand the common methods of high availability of microservices