AWS has many data centers on various geographic locations on this earth. AWS has categorized them into the regions and then further in availability zones.
Regions are the physical locations around the world where AWS has its datacenters.
But AWS does not keep a single data center in a region, instead, it keeps multiple datacenters inside a region and those data centers are further grouped together to make an Availability Zone.
It means that a Region can have multiple Availability Zones and each Availability Zone can further have one or more datacenter.
An Availability Zone can be considered as a collection of one more datacenter inside the same region.
- All AZs within the same region are interconnected with high internet bandwidth and low latency networking.
- Each AZ is physically separated by another AZ within the same region, but all AZs are within 100 KM of each other. This guarantees that failure of any one AZ due to any natural crisis such as flood, thunderstorm, earthquake, or by any human error would not affect the other one.
Deploying applications and databases in multiple AZs has certain benefits:
- Increased availability - High availability because of fault-tolerant behavior. For example, even if one AZ destroyed completely due to some natural disaster, your data will be secure and remain available in other AZ.
- Scalability - Scalability due to load distribution.
- Automatic failover to standby (Database) – Automatic failover to standby. (A failover is done when the primary database fails or has become unreachable and one of the standby databases is transitioned to take over the primary role.)