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 = 'en' 
WHERE 
  pfv.feature_id IN (
    20949, 24191, 20953, 24227, 23726, 24794, 
    24795, 24796, 24793
  ) 
  AND pfv.product_id IN (
    20838, 41136, 41146, 2623, 37897, 37890, 
    41126, 41107, 41129, 41425, 36522, 
    47432, 37891, 37883, 37884, 41132, 
    41118, 41120, 37893, 41109, 47433, 
    47415, 47430
  ) 
  AND pfv.lang_code = 'en'

Query time 0.00549

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": 228,
          "filtered": 0.660855412,
          "attached_condition": "pfv.feature_id in (20949,24191,20953,24227,23726,24794,24795,24796,24793) and pfv.product_id in (20838,41136,41146,2623,37897,37890,41126,41107,41129,41425,36522,47432,37891,37883,37884,41132,41118,41120,37893,41109,47433,47415,47430) and pfv.lang_code = 'en'",
          "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 = 'en'"
        }
      }
    ]
  }
}