Blob & Object Storage

// S3 object structure
// Bucket: my-app-assets
// Key: uploads/users/u-42/avatar.jpg
// → Not a real folder structure, just a key string
//
// Object has:
//   Key:      uploads/users/u-42/avatar.jpg
//   Data:     (binary content)
//   Metadata: Content-Type: image/jpeg, x-amz-meta-user-id: u-42
//   Size:     up to 5 TB per object
//   ETag:     MD5 hash for integrity

// S3 durability: 99.999999999% (11 nines)
// = losing 1 object out of 100 billion per year
// Achieved via automatic replication across 3+ AZs

// AWS SDK upload example (Java)
s3Client.putObject(
    PutObjectRequest.builder()
        .bucket("my-app-assets")
        .key("uploads/users/u-42/avatar.jpg")
        .contentType("image/jpeg")
        .build(),
    RequestBody.fromFile(avatarFile)
);

// Pre-signed URL — temporary access to private object
URL presignedUrl = s3Presigner.presignGetObject(
    GetObjectPresignRequest.builder()
        .signatureDuration(Duration.ofMinutes(15))
        .getObjectRequest(r -> r.bucket("private-docs").key("reports/q1.pdf"))
        .build()
).url();
// Returns: https://private-docs.s3.amazonaws.com/reports/q1.pdf?X-Amz-Signature=...
// Valid for 15 minutes, no AWS credentials needed by client

// S3 + CloudFront architecture for static assets
//  User → CloudFront (CDN edge) → S3 (origin)
//  First request: CDN fetches from S3, caches at edge
//  Subsequent:    Served from edge cache (< 20ms)

// Lifecycle policy — automatic cost optimisation
// Day 0–30:   S3 Standard ($0.023/GB)
// Day 31–90:  S3 Standard-IA ($0.0125/GB)
// Day 91–365: S3 Glacier ($0.004/GB)
// Day 366+:   S3 Glacier Deep Archive ($0.00099/GB)