Eventual Consistency Latency in IBM Cloud Object Storage Cross-Region Buckets

Concurrent Update Behavior

IBM Cloud Object Storage (COS) provides strong read-after-write consistency for the creation of new objects. However, updates to existing objects follow an eventual consistency model. In high-concurrency scenarios where multiple PUT requests target the same object key, the system employs a "Last-Writer-Wins" resolution strategy.

Cross-Region Propagation Uncertainty

When utilizing Cross-Region buckets, metadata updates and object version propagation must synchronize across geographically distributed clusters. There is an unresolved technical uncertainty regarding the specific propagation delay for these updates when requests are initiated from different regional endpoints during concurrent write operations.

This behavior can lead to situations where a GET request retrieves a stale version of an object despite a successful PUT response from a different region.

• What is the documented maximum propagation window for metadata updates in a Cross-Region bucket under heavy concurrent load?
• Does the latency for observing the latest version vary predictably based on the distance between the writing and reading endpoints?