Art of Codeartofcode
Lesson 15 of 16

11. Object / Blob Storage

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The picture to keep in your head
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11.1 What's the difference between block, file and object storage?
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11.2 Why not just store files in the database?
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11.3 What are buckets, keys and metadata?
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11.4 How do uploads work with presigned URLs?
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11.5 How do you upload very large files reliably?
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11.6 How does object storage avoid losing files?
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11.7 What are storage classes and lifecycle rules?
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11.8 How should files be served to users?
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11.9 What happens after a file is uploaded?
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Memory card and where the analogy breaks
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Practice: five levels
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Interview questions
14
Solutions
15
Sources
16
Code lab
11. Object / Blob Storage

Sources

3 min read+10 XP

Source notes

  • Amazon S3 multipart limits (5 MiB to 5 GiB per part, up to 10,000 parts, maximum object size 48.8 TiB) and the recommendation to use multipart for objects of about 100 MB and larger: AWS documentation, "Amazon S3 multipart upload limits" (https://docs.aws.amazon.com/AmazonS3/latest/userguide/qfacts.html), checked 2026-10-08.
  • S3 durability design target (99.999999999%) and storage across multiple Availability Zones for S3 Standard: AWS S3 documentation and product pages.
  • S3 strong read-after-write consistency since December 2020: AWS announcement, "Amazon S3 now delivers strong read-after-write consistency", December 2020.
  • Presigned URLs signed with Signature Version 4 can be valid for at most 7 days: AWS S3 documentation on presigned URLs.
  • Storage classes: AWS S3 and Google Cloud Storage documentation (class names as listed; prices and minimum durations change, check current pages).
  • The 10 + 4 erasure-coding layout is an illustrative example of the technique, not a specific provider's configuration.
  • Level 2 numbers are illustrative assumptions; arithmetic computed 2026-10-08.
  • Level 3 and Level 4 code: tested 2026-10-08 (code/ch11_blob_storage.py, all checks pass).