AWS, Azure & GCP · Cloud across providers

What is object storage and when should you use it?

Easyobject storages3storageUpdated Oct 2026

Short answer

Object storage stores immutable blobs with metadata in a flat namespace, accessed over HTTP APIs by key. It scales cheaply for backups, media, logs and data lakes, but is not a filesystem or a database.

Objects are written as whole units and addressed by a key inside a bucket or container. The provider replicates them across devices and zones for durability. You do not mount object storage as a normal disk or update bytes in place.

Features that matter

Durability and versioning to recover from overwrites and deletes
Lifecycle rules to transition older data to cheaper classes and expire it
Storage classes for hot, infrequent, archive and deep-archive access
Bucket policies, encryption, access points and signed URLs for controlled sharing
Event notifications to trigger processing when an object lands

json

{
  "Rules": [
    {
      "ID": "archive-logs",
      "Filter": { "Prefix": "logs/" },
      "Status": "Enabled",
      "Transitions": [
        { "Days": 30, "StorageClass": "STANDARD_IA" },
        { "Days": 180, "StorageClass": "GLACIER" }
      ],
      "Expiration": { "Days": 365 }
    }
  ]
}

A lifecycle policy that moves logs to cheaper tiers and expires them.

Object storage is eventually consistent for some operations depending on the provider and feature, and listing large buckets is expensive. Design keys and prefixes so that listing and analytics do not become the bottleneck.

Do not put a transactional database on object storage or assume POSIX semantics. If you need random writes and file locking, use block or file storage.

Follow-ups you should expect

Interviewers use these to check whether the first answer was understanding or memorisation.

1When would you use versioning and object lock?
2How do lifecycle rules reduce cost?
3Why is object storage a poor fit for a transactional database?
4How do you share a private object temporarily?

Say it in the interview

Object storage keeps whole blobs with metadata, addressed by key over an HTTP API. It is cheap and durable for backups, media, logs and data lakes, and features like versioning and lifecycle rules matter for operations. I do not treat it as a filesystem or database because it lacks in-place random writes and POSIX semantics.

Use this as a model, not a script. Saying it in your own words is what makes it survive follow-up pressure.

Now say it out loud.

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Features that matter

Follow-ups you should expect

Related questions

Now say it out loud.