SELECT 
  pfv.feature_id, 
  pfv.product_id, 
  pfv.variant_id, 
  fv.position, 
  fvd.variant 
FROM 
  cscart_product_features_values AS pfv 
  INNER JOIN cscart_product_feature_variants AS fv ON pfv.feature_id = fv.feature_id 
  AND pfv.variant_id = fv.variant_id 
  INNER JOIN cscart_product_feature_variant_descriptions AS fvd ON pfv.variant_id = fvd.variant_id 
  AND fvd.lang_code = 'vi' 
WHERE 
  pfv.feature_id IN (
    20011, 20001, 20005, 23357, 20861, 20260, 
    25022, 25021, 23927, 23536, 23537, 
    20879, 20261, 19627, 20234, 25095, 
    25096, 21054, 20003, 21021, 20259, 
    23415
  ) 
  AND pfv.product_id IN (
    5546, 5556, 16607, 6060, 2920, 4440, 
    27357, 38152, 35249, 2932, 18258, 14822, 
    18201, 40824, 2461, 5554, 2505, 4441, 
    33177
  ) 
  AND pfv.lang_code = 'vi'

Query time 0.01794

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "variant_id",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["feature_id", "product_id"],
          "rows": 453,
          "filtered": 0.059458815,
          "attached_condition": "pfv.feature_id in (20011,20001,20005,23357,20861,20260,25022,25021,23927,23536,23537,20879,20261,19627,20234,25095,25096,21054,20003,21021,20259,23415) and pfv.product_id in (5546,5556,16607,6060,2920,4440,27357,38152,35249,2932,18258,14822,18201,40824,2461,5554,2505,4441,33177) and pfv.lang_code = 'vi'",
          "using_index": true
        }
      },
      {
        "table": {
          "table_name": "fv",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY", "feature_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "ref": ["dev_db.pfv.variant_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "fv.feature_id = pfv.feature_id"
        }
      },
      {
        "table": {
          "table_name": "fvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "fvd.lang_code = 'vi'"
        }
      }
    ]
  }
}