AWS S3 (Simple Storage Service) is an Amazon foundational service for easy management of any size data. This 3-minute read explains the nuances of the four different flavors of S3.
S3 Standard is the default option upon which entire companies are built. It is used for image storage, content distribution, mobile, gaming, to Big Data analytics, data warehousing, and all sorts of cloud backups. Its core features are
- low latency (ms range) with high throughput
- 11-9 durability, i.e. 99.999999999% chance of survival, data spread across different Availability Zones (AZ) of a region 
- 99.99% availability over a year
- encryption in transit (SSL) and at rest
- configurable automatic lifecycle management, e.g. to archive data after 30 days
- $0.023 / GB month ²
S3 Standard-Infrequent Access (IA)
S3 Standard-IA has all features identical to S3 Standard, except for a lower availability at 99.9%. The price per GB is only half of that of S3 Standard, but there is an additional per GB retrieval fee. This storage class works well for data that needs to remain accessible quickly but infrequently, e.g. the backup for a disaster recovery system. S3 Standard-IA is configured at the object level; it can be used as lifecycle setting within an S3 Standard bucket.
S3 One Zone-IA (since April 2018)
S3 One Zone-IA has latency, throughput, and durability identical to S3 Standard-IA, except data is stored in only one Availability Zone (AZ) instead of 3 or more. This reduces overall availability to 99.5%, but also affords an additional cost savings of 20%. Complete data loss is possible if the entire AZ is lost in a catastrophic event like fire, earthquake, or flood. S3 One Zone-IA is an economic choice for secondary backups and any easily re-computable data. One has to weigh the cost savings of this option against the time and cost for rebuilding the data times the likelihood of such catastrophic event.
The opposite of a hot backup is the icy cold AWS Glacier³, the ideal solution for long-term data archiving needs. With a cost of $ 0.0005 / GB month it is 46 times cheaper than S3 Standard. There are three options to retrieve the archives with access times from minutes to hours. It is the perfect solution for long-term data archiving for legal and compliance reasons. Glacier can be configured to be the target destination of an automated lifecycle policy for the other three options above.
 Exact pricing varies slightly by region and usage tiers, see https://aws.amazon.com/s3/pricing
 AWS Regions consists of three or more physical data centers typically up to a hundred miles apart, a.k.a. Availability Zones (AZ).by