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SELECT 
  cscart_product_features.feature_id, 
  cscart_product_features.feature_code, 
  cscart_product_features.company_id, 
  cscart_product_features.feature_type, 
  cscart_product_features.parent_id, 
  cscart_product_features.display_on_product, 
  cscart_product_features.display_on_catalog, 
  cscart_product_features.display_on_header, 
  cscart_product_features_descriptions.description, 
  cscart_product_features_descriptions.internal_name, 
  cscart_product_features_descriptions.lang_code, 
  cscart_product_features_descriptions.prefix, 
  cscart_product_features_descriptions.suffix, 
  cscart_product_features.categories_path, 
  cscart_product_features_descriptions.full_description, 
  cscart_product_features.status, 
  cscart_product_features.comparison, 
  cscart_product_features.position, 
  cscart_product_features.purpose, 
  cscart_product_features.feature_style, 
  cscart_product_features.filter_style, 
  cscart_product_features.cp_ls_use 
FROM 
  cscart_product_features 
  LEFT JOIN cscart_product_features_descriptions ON cscart_product_features_descriptions.feature_id = cscart_product_features.feature_id 
  AND cscart_product_features_descriptions.lang_code = 'de' 
WHERE 
  cscart_product_features.feature_id = 327

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "const_condition": "1",
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_features",
          "access_type": "const",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["feature_id"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "cscart_product_features_descriptions",
          "access_type": "const",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["feature_id", "lang_code"],
          "ref": ["const", "const"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}

Result

feature_id	feature_code	company_id	feature_type	parent_id	display_on_product	display_on_catalog	display_on_header	description	internal_name	lang_code	prefix	suffix	categories_path	full_description	status	comparison	position	purpose	feature_style	filter_style	cp_ls_use
327		1	E	326	Y	Y	N	Brand Name	Brand Name	de			43210		A	N	0	organize_catalog	brand	checkbox	N