SELECT 
  c.* 
FROM 
  cscart_bm_containers as c 
WHERE 
  1 
  AND c.location_id = 4

Query time 0.00016

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "c",
      "access_type": "ref",
      "possible_keys": ["location_id"],
      "key": "location_id",
      "key_length": "3",
      "used_key_parts": ["location_id"],
      "ref": ["const"],
      "rows": 4,
      "filtered": 100
    }
  }
}