SELECT 
  c.* 
FROM 
  cscart_bm_containers as c 
WHERE 
  1 
  AND c.location_id = 20

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "c",
          "access_type": "ref",
          "possible_keys": [
            "location_id",
            "location_id_company_id",
            "location_id_position_company_id"
          ],
          "key": "location_id_company_id",
          "key_length": "3",
          "used_key_parts": ["location_id"],
          "ref": ["const"],
          "rows": 3,
          "filtered": 100
        }
      }
    ]
  }
}