Simple ElasticSearch autocomplete example configuration. The 'autocomplete' functionality is accomplished by lowercasing, character folding and n-gram tokenization of a specific indexed field (in this case "city").

es_simple_autocomplete_example_config.sh

# Delete the possibly existing autocomplete test index
curl -X DELETE localhost:9200/autocomplete_test

# Put the config of the autocomplete index
curl -X PUT localhost:9200/autocomplete_test -d '
{
  "settings" : {
    "index" : {
      "analysis" : {
        "analyzer" : {
          "autocomplete_analyzer" : {
            "type" : "custom",
            "tokenizer" : "lowercase",
            "filter"    : ["asciifolding", "title_ngram"]
          }
        },
        "filter" : {
          "title_ngram" : {
            "type" : "nGram",
            "min_gram" : 3,
            "max_gram" : 5
          }
        }
      }
    }
  },
 
  "mappings": {
    "city": {
      "properties": {
        "city": {
          "type": "string",
          "analyzer": "autocomplete_analyzer",
          "boost": 10
        }
      }
    }
  }
}
'

# Show how query input is analyzed
curl "http://localhost:9200/autocomplete_test/_analyze?text=Ouderkerk+aan+de+Amstel&analyzer=autocomplete_analyzer&pretty=True"


# Post some sample documents
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Amsterdam" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Amstelveen" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Ouderkerk aan de Amstel" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Alphen aan den Rijn" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Den Haag" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Rotterdam" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Groningen" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Castelré" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Etten-Leur" }'
curl -X POST "http://localhost:9200/autocomplete_test/city" -d '{ "city" : "Babyloniënbroek" }'

# Make sure everything is indexed
curl -X POST "http://localhost:9200/autocomplete_test/_refresh"

# Perform some searches
curl "http://localhost:9200/autocomplete_test/_search?q=city:Ams&pretty=True"
curl "http://localhost:9200/autocomplete_test/_search?q=city:aan+de&pretty=True"
curl "http://localhost:9200/autocomplete_test/_search?q=city:etten&pretty=True"
curl "http://localhost:9200/autocomplete_test/_search?q=city:lre&pretty=True"

You should use a different search analyzer, also, this is matching all words, not only the first one.