CONCEPT Cited by 1 source

Index alias

An index alias in OpenSearch/Elasticsearch is a stable name (pointer) that maps to one or more underlying indices. Aliases can be atomically swapped to point at a different index, enabling zero-downtime migrations and blue-green index deployments.

Properties

• Atomic swap — a single API call moves the alias from old to new index with no window where neither is attached.
• Write alias — can designate a single index as the write target while multiple indices serve reads.
• Filter alias — can include a query filter, restricting the visible subset of documents.
• Routing alias — can include routing values for multi-tenant indices.

Role in Zero-Downtime Migration

AOSC relies on index aliases for the cutover step: after backfill, replay, and convergence, the coordinator swaps the alias from source to target in one atomic operation. This is only possible because Atlassian's Search Platform already routes all traffic through aliases rather than concrete index names.

Prerequisite

Applications must address indices through aliases (not bare index names) for alias-based cutover to work. Retrofitting this on an existing system that uses concrete names requires its own migration step.

Seen In

• systems/opensearch-aosc — relies on alias swap for atomic cutover
• sources/2026-07-24-atlassian-online-index-migration-and-shard-scaling-in-opensearch-with-aosc

(Source: sources/2026-07-24-atlassian-online-index-migration-and-shard-scaling-in-opensearch-with-aosc)