SELECT 
  company_id 
FROM 
  cscart_companies 
WHERE 
  status = 'A'

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0136258,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_companies",
          "access_type": "ALL",
          "loops": 1,
          "rows": 17,
          "cost": 0.0136258,
          "filtered": 100,
          "attached_condition": "cscart_companies.`status` = 'A'"
        }
      }
    ]
  }
}