How-To Guides on Advanced Beginner

Slow Query Optimization

d8lzz1gpw@mozmail.com (kimbenji) — Fri, 16 Jan 2026 00:00:00 +0000

Learn how to diagnose and improve slow search response times.

Duration: Approximately 15-30 minutes

Scope of This Guide
Covered: Query-level performance optimization, Profile API analysis, cache utilization

Not Covered: Cluster-level tuning (adding nodes, hardware upgrades) - see Performance Tuning

TL;DR

Analyze query execution plans with Profile API

Remove unnecessary fields: _source filtering, stored fields

Optimize query types: Use term instead of match, avoid leading wildcards

Leverage caching: Use filter context, enable request cache

Before You Begin#

Verify the following requirements:

Memory Troubleshooting

d8lzz1gpw@mozmail.com (kimbenji) — Fri, 16 Jan 2026 00:00:00 +0000

Learn how to diagnose and resolve OutOfMemoryError and GC issues.

Duration: Approximately 20-40 minutes (additional 10 minutes for GC log analysis)

Scope of This Guide
Covered: Heap memory settings, Circuit Breaker, Field Data optimization, GC tuning

Not Covered: Adding nodes, hardware upgrades - see Cluster Management

TL;DR

Heap memory: 50% or less of total memory, maximum 31GB

Circuit Breaker: Check settings to prevent memory overuse

Field data: Avoid aggregations on text fields, use doc_values

GC tuning: Use G1GC, analyze logs to identify issues

Before You Begin#

Verify the following requirements:

Mapping Migration

d8lzz1gpw@mozmail.com (kimbenji) — Mon, 23 Mar 2026 00:00:00 +0000

This guide walks you through changing index mappings (field types, analyzers, etc.) without downtime.

Estimated time: About 20-40 minutes (additional time may be required depending on data size)

Scope of This Guide
Covers: Zero-downtime mapping changes using the Reindex API, Alias switching strategy, and validation methods

Does not cover: For large-scale index rebuilds, see Index Rebuild. For cluster-level changes, see Cluster Scaling.

TL;DR

Alias-based operations: Your application accesses indices through Aliases

Create new index: Create a new index with the updated mapping and Reindex

Switch Alias: After validation, switch the Alias to the new index

Rollback ready: You can roll back instantly as long as you don’t delete the old index

Before You Begin#

Verify the following prerequisites:

Index Rebuild

d8lzz1gpw@mozmail.com (kimbenji) — Mon, 23 Mar 2026 00:00:00 +0000

This guide walks you through efficiently rebuilding large indices.

Estimated time: About 30-60 minutes (may take several hours depending on data size)

Scope of This Guide
Covers: _reindex API, Snapshot/Restore, Logstash comparison, large-scale processing strategies, and performance optimization

Does not cover: For simple mapping changes, see Mapping Migration. For cluster scaling, see Cluster Scaling.

TL;DR

_reindex API: Simplest option, best for rebuilds within the same cluster

Snapshot/Restore: Best for cross-cluster migration and very large datasets

Logstash: Best for complex transformations or external source integration

Performance optimization: Use refresh_interval: -1, replica 0, and sliced scroll

Before You Begin#

Verify the following prerequisites:

Cluster Scaling

d8lzz1gpw@mozmail.com (kimbenji) — Mon, 23 Mar 2026 00:00:00 +0000

This guide walks you through safely scaling an Elasticsearch cluster.

Estimated time: About 30-60 minutes (additional time for node addition and shard rebalancing)

Scope of This Guide
Covers: Adding data nodes, role-based node separation, Hot-Warm-Cold architecture, and post-scaling validation

Does not cover: For query-level performance optimization, see Slow Query Optimization. For memory issues, see Memory Troubleshooting.

TL;DR

Horizontal scaling: Add data nodes and rebalance shards

Role separation: Separate master, data, coordinating, and ingest nodes for stability

Hot-Warm-Cold: Tier nodes by data access frequency for cost optimization

Post-scaling validation: Always verify cluster status, shard distribution, and performance metrics

Before You Begin#

Verify the following prerequisites: