S3 Service Limitations

Constraints & Boundaries

Bucket Limitations

Bucket Count

100 buckets per AWS account (soft limit)

Bucket Names

3-63 characters, globally unique, DNS-compliant

Objects per Bucket

Virtually unlimited number of objects

Object Limitations

Object Size

0 bytes to 5 TB maximum

Single PUT Limit

5 GB maximum per PUT request

Key Length

1-1024 UTF-8 characters

Metadata

2 KB maximum per object

Request Rate Limits

GET/HEAD Requests

5,500 requests per second per prefix

  • • Scales automatically
  • • Per prefix performance
  • • No pre-warming needed

PUT/COPY/POST/DELETE

3,500 requests per second per prefix

  • • Write operations
  • • Automatic scaling
  • • Prefix distribution important

LIST Operations

Limited by response size and complexity

  • • 1000 objects per response
  • • Use pagination for large lists
  • • Consider prefix organization

Multipart Upload Limits

Maximum Parts

10,000 parts per upload

Part Size Range

5 MB to 5 GB per part

Last Part Exception

Last part can be smaller than 5 MB

Tagging Limitations

Tags per Object

10 tags maximum per object

Key Length

128 Unicode characters maximum

Value Length

256 Unicode characters maximum

Regional and Service Limits

Event Notifications

1000 configurations per bucket

Lifecycle Rules

1000 rules per bucket

CORS Rules

100 rules per bucket

Replication Rules

1000 rules per bucket

Common Issues

Hot Spotting

Sequential naming patterns cause performance issues

Request Rate Exceeded

Too many requests to single prefix

Bucket Name Conflicts

Globally unique naming requirement

Workarounds

Random Prefixes

Use random characters to distribute load

Request Retry Logic

Implement exponential backoff

Multiple Buckets

Distribute load across buckets

Service Quotas and Adjustments

Adjustable Limits

  • • Bucket count (default 100, can be increased)
  • • Request rate limits (automatic scaling)
  • • Some regional service limits

Hard Limits

  • • Object size (5 TB maximum)
  • • Single PUT request (5 GB maximum)
  • • Multipart upload parts (10,000 maximum)
  • • Bucket naming constraints

S3 Limitations Exam Tips

  • • Objects can be 0 bytes to 5 TB, but single PUT is limited to 5 GB
  • • Use multipart upload for objects larger than 100 MB
  • • Bucket names must be globally unique and DNS-compliant
  • • S3 automatically scales to handle high request rates
  • • Avoid sequential naming patterns to prevent hot spotting
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