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 (
    21384, 25127, 25035, 21140, 22654, 23540, 
    24831, 24631, 24717, 19582, 20835, 
    24957, 19777, 21386, 24144, 25095, 
    19725, 23544, 24832, 20381, 21914, 
    20084
  ) 
  AND pfv.product_id IN (
    1896, 50216, 49588, 2320, 2319, 35256, 
    47632, 45283, 46822, 6659, 50182, 48823, 
    15457, 1894, 49873, 6357, 35279, 47597, 
    18608, 1057, 17265
  ) 
  AND pfv.lang_code = 'vi'

Query time 0.02687

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": 490,
          "filtered": 0.11477302,
          "attached_condition": "pfv.feature_id in (21384,25127,25035,21140,22654,23540,24831,24631,24717,19582,20835,24957,19777,21386,24144,25095,19725,23544,24832,20381,21914,20084) and pfv.product_id in (1896,50216,49588,2320,2319,35256,47632,45283,46822,6659,50182,48823,15457,1894,49873,6357,35279,47597,18608,1057,17265) 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'"
        }
      }
    ]
  }
}