SELECT 
  s.*, 
  d.slide_name 
FROM 
  cscart_aprilec_print_slides s 
  LEFT JOIN cscart_aprilec_print_slide_descriptions d ON s.slide_id = d.slide_id 
  AND d.lang_code = 'en' 
WHERE 
  s.product_id = 12 
  AND s.status = 'A' 
ORDER BY 
  s.position, 
  s.slide_id

Query time 0.00052

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "ordering_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "s",
            "access_type": "system",
            "possible_keys": [
              "product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "0.20",
              "prefix_cost": "0.00",
              "data_read_per_join": "32"
            },
            "used_columns": [
              "slide_id",
              "product_id",
              "image_id",
              "position",
              "status",
              "is_required",
              "timestamp"
            ]
          }
        },
        {
          "table": {
            "table_name": "d",
            "access_type": "const",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "slide_id",
              "lang_code"
            ],
            "key_length": "10",
            "ref": [
              "const",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "0.20",
              "prefix_cost": "0.00",
              "data_read_per_join": "784"
            },
            "used_columns": [
              "slide_id",
              "lang_code",
              "slide_name"
            ]
          }
        }
      ]
    }
  }
}