What are the S3 Glacier storage classes and how do their retrieval times differ?
Glacier Instant Retrieval returns data in milliseconds. Glacier Flexible Retrieval takes minutes to hours depending on the option. Glacier Deep Archive is the cheapest and takes hours, typically around 12 hours or more.
Explain it simply
Think of three storage rooms. Instant Retrieval is the cupboard in your own room: archived but easy to open. Flexible Retrieval is the college store room where you request the key and wait a few hours. Deep Archive is a warehouse in another city: cheapest of all, but a full day to get things back.
Example
Glacier Instant Retrieval : milliseconds, min storage 90 days
for archives read about once a quarter
Glacier Flexible Retrieval: Expedited 1-5 minutes
Standard 3-5 hours
Bulk 5-12 hours (cheapest)
min storage 90 days
Glacier Deep Archive : Standard ~12 hours, Bulk ~48 hours
min storage 180 days, lowest costColder classes cost less to store but more to retrieve and carry minimum storage durations: delete early and you are still billed for the full period.
For Flexible Retrieval and Deep Archive, you first request a restore, which makes a temporary copy available for the number of days you choose. Typical uses: compliance records kept for years, old medical images, raw footage that is rarely needed again.
What to say in the interview
"Instant Retrieval gives millisecond access for rarely read archives, Flexible Retrieval takes minutes to hours depending on the tier, and Deep Archive is the cheapest with around 12 to 48 hours. Colder means cheaper storage but costlier, slower retrieval and minimum durations, so I match the class to how often the data is really needed."
Common mistakes
- Moving data you read weekly into Deep Archive to save storage cost.