SELECT 
  n.sf_id, 
  n.features_hash, 
  n.show_in_breadcrumbs, 
  nd.product_breadcrumb 
FROM 
  cscart_ab__sf_names as n 
  INNER JOIN cscart_ab__sf_name_descriptions as nd ON (
    nd.sf_id = n.sf_id 
    AND nd.lang_code = 'ru'
  ) 
WHERE 
  (
    (
      LENGTH(n.features_hash)= 6 
      AND LOCATE('2-8883', n.features_hash) > 0
    )
  ) 
  AND n.category_id = 48 
  AND n.fixed in ('F', 'U') 
  AND n.company_id = 1

Query time 0.00069

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "0.70"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "nd",
          "access_type": "ALL",
          "possible_keys": [
            "PRIMARY"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.25",
            "eval_cost": "0.10",
            "prefix_cost": "0.35",
            "data_read_per_join": "6K"
          },
          "used_columns": [
            "sf_id",
            "lang_code",
            "product_breadcrumb"
          ],
          "attached_condition": "(`testdobroded`.`nd`.`lang_code` = 'ru')"
        }
      },
      {
        "table": {
          "table_name": "n",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY",
            "fixed_category_hash"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "sf_id"
          ],
          "key_length": "4",
          "ref": [
            "testdobroded.nd.sf_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.25",
            "eval_cost": "0.10",
            "prefix_cost": "0.70",
            "data_read_per_join": "344"
          },
          "used_columns": [
            "sf_id",
            "category_id",
            "features_hash",
            "fixed",
            "company_id",
            "show_in_breadcrumbs"
          ],
          "attached_condition": "((`testdobroded`.`n`.`company_id` = 1) and (`testdobroded`.`n`.`category_id` = 48) and (length(`testdobroded`.`n`.`features_hash`) = 6) and (locate('2-8883',`testdobroded`.`n`.`features_hash`) > 0) and (`testdobroded`.`n`.`fixed` in ('F','U')))"
        }
      }
    ]
  }
}