SELECT 
  cscart_product_feature_variant_descriptions.variant, 
  cscart_product_feature_variants.variant_id, 
  cscart_product_feature_variants.feature_id, 
  cscart_product_features_values.variant_id as selected, 
  cscart_product_features.feature_type, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path 
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 = 'en' 
  INNER JOIN cscart_product_features_values ON cscart_product_features_values.variant_id = cscart_product_feature_variants.variant_id 
  AND cscart_product_features_values.lang_code = 'en' 
  AND cscart_product_features_values.product_id = 76 
  AND cscart_product_features_values.feature_id = cscart_product_feature_variants.feature_id 
  LEFT JOIN cscart_product_features ON cscart_product_features.feature_id = cscart_product_feature_variants.feature_id 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = cscart_product_feature_variants.variant_id 
  AND cscart_seo_names.type = 'e' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'en' 
WHERE 
  1 
  AND cscart_product_feature_variants.feature_id IN (18, 15, 16, 17) 
GROUP BY 
  cscart_product_feature_variants.variant_id 
ORDER BY 
  cscart_product_feature_variants.position, 
  cscart_product_feature_variant_descriptions.variant

Query time 0.00111

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "8.98"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": false,
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_features_values",
              "access_type": "range",
              "possible_keys": [
                "PRIMARY",
                "fl",
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              ],
              "key": "idx_product_feature_variant_id",
              "used_key_parts": [
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                "feature_id",
                "lang_code"
              ],
              "key_length": "12",
              "rows_examined_per_scan": 4,
              "rows_produced_per_join": 4,
              "filtered": "100.00",
              "using_index": true,
              "cost_info": {
                "read_cost": "1.93",
                "eval_cost": "0.80",
                "prefix_cost": "2.73",
                "data_read_per_join": "3K"
              },
              "used_columns": [
                "feature_id",
                "product_id",
                "variant_id",
                "lang_code"
              ],
              "attached_condition": "((`danishecarter_31jan`.`cscart_product_features_values`.`product_id` = 76) and (`danishecarter_31jan`.`cscart_product_features_values`.`feature_id` in (18,15,16,17)) and (`danishecarter_31jan`.`cscart_product_features_values`.`lang_code` = 'en'))"
            }
          },
          {
            "table": {
              "table_name": "cscart_product_feature_variants",
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              "possible_keys": [
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              "key": "PRIMARY",
              "used_key_parts": [
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              "ref": [
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              "rows_produced_per_join": 0,
              "filtered": "5.00",
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              "used_columns": [
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              "attached_condition": "(`danishecarter_31jan`.`cscart_product_feature_variants`.`feature_id` = `danishecarter_31jan`.`cscart_product_features_values`.`feature_id`)"
            }
          },
          {
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              "used_columns": [
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          },
          {
            "table": {
              "table_name": "cscart_product_feature_variant_descriptions",
              "access_type": "eq_ref",
              "possible_keys": [
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              "key": "PRIMARY",
              "used_key_parts": [
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              ],
              "key_length": "9",
              "ref": [
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                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 0,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.20",
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                "data_read_per_join": "619"
              },
              "used_columns": [
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                "variant",
                "lang_code"
              ]
            }
          },
          {
            "table": {
              "table_name": "cscart_seo_names",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "dispatch"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
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              ],
              "key_length": "206",
              "ref": [
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              ],
              "rows_examined_per_scan": 4,
              "rows_produced_per_join": 0,
              "filtered": "100.00",
              "cost_info": {
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                "prefix_cost": "8.99",
                "data_read_per_join": "1K"
              },
              "used_columns": [
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                "object_id",
                "type",
                "dispatch",
                "path",
                "lang_code"
              ]
            }
          }
        ]
      }
    }
  }
}