Question from the Elasticsearch test

POST /people/_search?size=0
{
  "agg": {
    "avg": { "field": "age" }
  }
}

POST /people/_search?size=0
{
  "agg": {
    "avg_age": { "avg": { "field": "age" } }
  }
}

POST /people/_search?size=0
{
  "aggs": {
    "avg": { "field": "age" }
  }
}

POST /people/_search?size=0
{
  "aggs": {
    "avg_age": { "avg": { "field": "age" } }
  }
}