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)= 5 
      AND LOCATE('10-89', n.features_hash) > 0
    )
  ) 
  AND n.category_id = 237 
  AND n.fixed in ('F', 'U') 
  AND n.company_id = 1

Query time 0.00005

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.05"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "n",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fixed_category_hash"
          ],
          "key": "fixed_category_hash",
          "used_key_parts": [
            "fixed",
            "category_id"
          ],
          "key_length": "7",
          "rows_examined_per_scan": 2,
          "rows_produced_per_join": 0,
          "filtered": "10.00",
          "index_condition": "((`44mm_ru`.`n`.`category_id` = 237) and (length(`44mm_ru`.`n`.`features_hash`) = 5) and (locate('10-89',`44mm_ru`.`n`.`features_hash`) > 0) and (`44mm_ru`.`n`.`fixed` in ('F','U')))",
          "cost_info": {
            "read_cost": "4.77",
            "eval_cost": "0.04",
            "prefix_cost": "4.81",
            "data_read_per_join": "68"
          },
          "used_columns": [
            "sf_id",
            "category_id",
            "features_hash",
            "fixed",
            "company_id",
            "show_in_breadcrumbs"
          ],
          "attached_condition": "(`44mm_ru`.`n`.`company_id` = 1)"
        }
      },
      {
        "table": {
          "table_name": "nd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "sf_id",
            "lang_code"
          ],
          "key_length": "10",
          "ref": [
            "44mm_ru.n.sf_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 0,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.20",
            "eval_cost": "0.04",
            "prefix_cost": "5.05",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "sf_id",
            "lang_code",
            "product_breadcrumb"
          ]
        }
      }
    ]
  }
}