Multipart upload allows large files to be uploaded in segments. Each part is stored individually until the upload is finalized by a “CompleteMultipartUpload” request. If this final request is never issued—due to a timeout, crash, failed job, or misconfiguration—the parts remain stored but are effectively useless: they do not form a valid object and cannot be retrieved. Without a lifecycle policy in place to clean up these incomplete uploads, the orphaned parts persist and continue to incur storage charges indefinitely.

S3 buckets often persist after projects complete or when the associated workloads have been retired. If a bucket is no longer being read from or written to—and its contents are not required for compliance, backup, or retention purposes—it represents ongoing cost without delivering value. Many organizations overlook these idle buckets, especially in shared or legacy accounts, leading to unnecessary storage costs over time.

Some S3 lifecycle policies are configured to transition objects from Standard storage to Intelligent-Tiering after a fixed number of days (e.g., 30 days). This creates a delay where objects reside in S3 Standard, incurring higher storage costs without benefit. Since Intelligent-Tiering does not require prior access history and can be used immediately, it is often more efficient to place objects directly into Intelligent-Tiering at the time of upload. Lifecycle transitions introduce unnecessary intermediate costs that can be avoided entirely through configuration changes.

S3 Standard is the default storage class and is often used by default even for data that is rarely accessed. Keeping large volumes of infrequently accessed data in S3 Standard leads to unnecessary costs. Data such as backups, logs, archives, or historical snapshots are often strong candidates for migration to colder tiers like S3 Glacier or Deep Archive. If access patterns are unknown or variable, S3 Intelligent-Tiering can reduce costs without requiring manual transitions.