SELECT 
  ab__dotd.*, 
  ab__dotd_desc.h1, 
  ab__dotd_desc.page_title, 
  ab__dotd_desc.meta_description, 
  ab__dotd_desc.meta_keywords 
FROM 
  cscart_ab__dotd AS ab__dotd 
  LEFT JOIN cscart_ab__dotd_descriptions AS ab__dotd_desc ON ab__dotd.promotion_id = ab__dotd_desc.promotion_id 
  AND ab__dotd_desc.lang_code = 'en' 
WHERE 
  ab__dotd.promotion_id = 23

Query time 0.00071

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "ab__dotd",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "promotion_id"
          ],
          "key_length": "3",
          "ref": [
            "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": "32"
          },
          "used_columns": [
            "promotion_id",
            "filter",
            "use_products_filter",
            "hide_products_block",
            "show_label_in_products_lists",
            "use_schedule",
            "ab__dotd_schedule"
          ]
        }
      },
      {
        "table": {
          "table_name": "ab__dotd_desc",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "promotion_id",
            "lang_code"
          ],
          "key_length": "9",
          "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": "3K"
          },
          "used_columns": [
            "promotion_id",
            "h1",
            "page_title",
            "meta_description",
            "meta_keywords",
            "lang_code"
          ]
        }
      }
    ]
  }
}