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SELECT 
  * 
FROM 
  cscart_product_feature_variants 
  LEFT JOIN cscart_product_feature_variant_descriptions ON cscart_product_feature_variant_descriptions.variant_id = cscart_product_feature_variants.variant_id 
  AND cscart_product_feature_variant_descriptions.lang_code = 'es' 
WHERE 
  cscart_product_feature_variants.variant_id = 108

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_feature_variants",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_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": "1K"
          },
          "used_columns": [
            "variant_id",
            "feature_id",
            "url",
            "color",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "cscart_product_feature_variant_descriptions",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_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": [
            "variant_id",
            "variant",
            "description",
            "page_title",
            "meta_keywords",
            "meta_description",
            "lang_code"
          ]
        }
      }
    ]
  }
}

Result

variant_id	feature_id	url	color	position	variant	description	page_title	meta_keywords	meta_description	lang_code
108	18			0	HTC	<p><p><b>HTC Corporation</b> is a Taiwanese manufacturer of smartphones and tablets headquartered in Taoyuan City, Taiwan. Initially making smartphones based mostly on Microsoft's Windows Mobile operating system (OS) software, HTC expanded its focus in 2009 to devices based on the Android OS, and in 2010 to Windows Phone OS.</p> <p>HTC is a member of the Open Handset Alliance, a group of handset manufacturers and mobile network operators dedicated to the development of the Android mobile device platform. The HTC Dream, marketed by T-Mobile in many countries as the T-Mobile G1 or Era G1, was the first phone on the market to use the Android mobile device platform.</p><br></p>				es