Elastic Cloud change history: Replication bug causing slow recoveries

Elastic Cloud Hosted reported major degradation from 2026-09-01 08:16 UTC to 2026-09-30 20:44 UTC (29 days 12 h). In Elasticsearch 9.5.0, 9.5.1 and 9.5.2, bulk indexing could cause replica divergence, high disk usage and long-running recoveries. Elastic fixed the bug in 9.5.3 and advised affected customers to upgrade and follow workaround steps.