Elasticsearch

Mapping

{
  "mappings": {
    "properties": {
      "title": {
        "type": "text",
        "analyzer": "english",
        "fields": {
          "keyword": { "type": "keyword" },
          "autocomplete": {
            "type": "text",
            "analyzer": "autocomplete_analyzer"
          }
        }
      },
      "description": { "type": "text", "analyzer": "english" },
      "price": { "type": "scaled_float", "scaling_factor": 100 },
      "category": { "type": "keyword" },
      "tags": { "type": "keyword" },
      "created_at": { "type": "date" },
      "location": { "type": "geo_point" },
      "in_stock": { "type": "boolean" }
    }
  }
}

Field Type Selection

Analyzers

{
  "settings": {
    "analysis": {
      "analyzer": {
        "autocomplete_analyzer": {
          "type": "custom",
          "tokenizer": "autocomplete_tokenizer",
          "filter": ["lowercase"]
        }
      },
      "tokenizer": {
        "autocomplete_tokenizer": {
          "type": "edge_ngram",
          "min_gram": 2,
          "max_gram": 20,
          "token_chars": ["letter", "digit"]
        }
      }
    }
  }
}

Sharding Strategy

2. Query DSL (CRITICAL)

Full-Text Search

{
  "query": {
    "bool": {
      "must": [
        {
          "multi_match": {
            "query": "wireless headphones",
            "fields": ["title^3", "description", "tags^2"],
            "type": "best_fields",
            "fuzziness": "AUTO"
          }
        }
      ],
      "filter": [
        { "term": { "category": "electronics" } },
        { "range": { "price": { "gte": 20, "lte": 200 } } },
        { "term": { "in_stock": true } }
      ],
      "should": [
        { "term": { "featured": { "value": true, "boost": 5 } } }
      ]
    }
  },
  "highlight": {
    "fields": { "title": {}, "description": {} }
  },
  "sort": [
    "_score",
    { "created_at": "desc" }
  ],
  "from": 0,
  "size": 20
}

Rule: Use filter for exact matches (no scoring, cached), must for relevance-scored text.

Autocomplete

{
  "query": {
    "match": {
      "title.autocomplete": {
        "query": "wire",
        "analyzer": "standard"
      }
    }
  },
  "_source": ["title", "category"],
  "size": 5
}

Aggregations

{
  "size": 0,
  "aggs": {
    "by_category": {
      "terms": { "field": "category", "size": 20 },
      "aggs": {
        "avg_price": { "avg": { "field": "price" } },
        "price_ranges": {
          "range": {
            "field": "price",
            "ranges": [
              { "to": 50 },
              { "from": 50, "to": 100 },
              { "from": 100 }
            ]
          }
        }
      }
    }
  }
}

3. Indexing Patterns

Bulk API

POST _bulk
{"index": {"_index": "products", "_id": "1"}}
{"title": "Wireless Headphones", "price": 79.99, "category": "electronics"}
{"index": {"_index": "products", "_id": "2"}}
{"title": "Running Shoes", "price": 129.99, "category": "sports"}

Index Lifecycle Management (ILM)

{
  "policy": {
    "phases": {
      "hot":   { "actions": { "rollover": { "max_size": "50gb", "max_age": "7d" } } },
      "warm":  { "min_age": "30d", "actions": { "shrink": { "number_of_shards": 1 }, "forcemerge": { "max_num_segments": 1 } } },
      "cold":  { "min_age": "90d", "actions": { "searchable_snapshot": { "snapshot_repository": "backups" } } },
      "delete": { "min_age": "365d", "actions": { "delete": {} } }
    }
  }
}

4. Common Anti-Patterns

1. Using ES as a primary database — it's a search engine, not ACID storage
2. Not setting explicit mappings — dynamic mapping guesses wrong types
3. Keyword fields for full-text search — use text with analyzers
4. Querying without filters — filters are cached and avoid scoring overhead
5. Too many shards — small indices need 1 shard; over-sharding wastes resources
6. Deep pagination with from+size — use search_after for >10K results
7. Not using bulk API — single-doc indexing is orders of magnitude slower
8. Wildcard queries on large fields — extremely expensive; use edge_ngram instead

References

• Elasticsearch Guide
• Query DSL
• Mapping Types
• Index Lifecycle Management