Elasticsearch 9

As of: 2025-04 (9.x through 2026)

What it delivers

• Performance/efficiency pass: meaningful heap reduction and better p99 latency on search-heavy workloads; better default behavior on modern JDKs (virtual-thread-aware client era).
• ESQL — the pipeline query language — keeps expanding: more aggregations, lookups, andFROM sources; it is the strategic analytics interface.
• Lucene 10 underneath; vector search (kNN/dense_vector) improvements continue at pace — hybrid BM25 + vector retrieval is first-class.
• Snapshot/restore and cross-cluster ops polish; 8→9 upgrade is a standard rolling reindex-free major (check plugin matrix).

Advice

If you left Elasticsearch during the license drama and run OpenSearch: both lines are healthy in 2026; the APIs diverged enough that switching costs real work — pick per org, not per team.