SELECT 
  profile_fields_data.field_id, 
  profile_fields_data.value, 
  profile_fields.field_type 
FROM 
  cscart_profile_fields_data AS profile_fields_data 
  LEFT JOIN cscart_profile_fields AS profile_fields ON profile_fields_data.field_id = profile_fields.field_id 
WHERE 
  object_id = 7 
  AND object_type = 'S'

Query time 0.00153

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "profile_fields_data",
          "access_type": "ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["object_id", "object_type"],
          "ref": ["const", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "profile_fields_data.object_type = 'S'"
        }
      },
      {
        "table": {
          "table_name": "profile_fields",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["field_id"],
          "ref": ["dev_db.profile_fields_data.field_id"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}